diff --git a/src/Oms.Application/Dtos/Orders/OpenApiParcelCreateInput.cs b/src/Oms.Application/Dtos/Orders/OpenApiParcelCreateInput.cs
index ccf50e9..dcfb695 100644
--- a/src/Oms.Application/Dtos/Orders/OpenApiParcelCreateInput.cs
+++ b/src/Oms.Application/Dtos/Orders/OpenApiParcelCreateInput.cs
@@ -8,9 +8,6 @@ namespace Oms.Application.Dtos.Orders;
 /// </summary>
 public class OpenApiParcelCreateInput
 {
-    /// <summary>请求标识（幂等，可选）。</summary>
-    public string? RequestId { get; set; }
-
     /// <summary>客户单号。</summary>
     public string? ClientNo { get; set; }
 
@@ -107,7 +104,7 @@ public class OpenApiParcelCreateInput
     public OrderParcelCreateInput ToOrderParcelCreateInput(int customerId) =>
         new()
         {
-            RequestId = RequestId,
+            RequestId = null,
             ClientNo = ClientNo,
             TrackNo = TrackNo,
             ServiceNo = ServiceNo,
diff --git a/src/Oms.Application/Services/OpenApi/OpenApiService.cs b/src/Oms.Application/Services/OpenApi/OpenApiService.cs
index 2b5c66f..0076fbb 100644
--- a/src/Oms.Application/Services/OpenApi/OpenApiService.cs
+++ b/src/Oms.Application/Services/OpenApi/OpenApiService.cs
@@ -1,5 +1,8 @@
+using System.Text;
+using System.Text.Json;
 using Fake.Application;
 using Microsoft.AspNetCore.Authorization;
+using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Mvc;
 using Oms.Application.Dtos.OpenApi;
 using Oms.Application.Dtos.Orders;
@@ -11,11 +14,16 @@ namespace Oms.Application.Services.OpenApi;
 /// <summary>
 /// 对外开放 API（Swagger 文档分组：openApi）。
 /// 统一响应：{ code, msg, data }。
-/// 客户机机鉴权：请求头 appKey + appSecret（勿放 Body，避免落日志）。
+/// 客户下单鉴权：Header appKey + timestamp + sign（HMAC-SHA256，5 分钟窗口）；Secret 不上传。
 /// </summary>
 [ApiExplorerSettings(GroupName = "openApi")]
 public class OpenApiService : ApplicationService
 {
+    private static readonly JsonSerializerOptions BodyJsonOptions = new()
+    {
+        PropertyNameCaseInsensitive = true
+    };
+
     private CustomerOpenApiAuthHelper AuthHelper =>
         LazyServiceProvider.GetRequiredService<CustomerOpenApiAuthHelper>();
 
@@ -25,6 +33,9 @@ public class OpenApiService : ApplicationService
     private OrderService OrderService =>
         LazyServiceProvider.GetRequiredService<OrderService>();
 
+    private IHttpContextAccessor HttpContextAccessor =>
+        LazyServiceProvider.GetRequiredService<IHttpContextAccessor>();
+
     /// <summary>
     /// 推送揽收件重尺并按当前产品计算应收应付（上游 itfx 鉴权后转发，无需客户凭证）。
     /// </summary>
@@ -52,20 +63,27 @@ public class OpenApiService : ApplicationService
 
     /// <summary>
     /// 创建订单包裹（仅自发货）。
-    /// 鉴权：Header appKey、appSecret；客户归属强制取自凭证，Body 不可指定 customerId。
+    /// Header：appKey、timestamp（Unix 秒）、sign。
+    /// sign = hex(HMAC-SHA256(appSecret, appKey + "\n" + timestamp + "\n" + sha256Hex(rawBody)))。
     /// </summary>
     [AllowAnonymous]
     [HttpPost("/openapi/parcel/create")]
     public async Task<OpenApiEnvelope<OrderParcelCreateOutput>> CreateParcelAsync(
         [FromHeader(Name = CustomerOpenApiAuthHelper.AppKeyHeaderName)] string? appKey,
-        [FromHeader(Name = CustomerOpenApiAuthHelper.AppSecretHeaderName)] string? appSecret,
-        [FromBody] OpenApiParcelCreateInput input)
+        [FromHeader(Name = CustomerOpenApiAuthHelper.TimestampHeaderName)] string? timestamp,
+        [FromHeader(Name = CustomerOpenApiAuthHelper.SignHeaderName)] string? sign)
     {
         try
         {
-            ArgumentNullException.ThrowIfNull(input);
+            var rawBody = await ReadRawBodyAsync();
+            var (customer, _) = await AuthHelper.ResolveSignedAsync(appKey, timestamp, sign, rawBody);
+
+            var input = JsonSerializer.Deserialize<OpenApiParcelCreateInput>(rawBody, BodyJsonOptions);
+            if (input == null)
+            {
+                throw new BusinessException("请求体不能为空");
+            }
 
-            var (customer, _) = await AuthHelper.ResolveAsync(appKey, appSecret);
             var data = await OrderService.CreateParcelAsync(input.ToOrderParcelCreateInput(customer.Id));
             return OpenApiEnvelope<OrderParcelCreateOutput>.Ok(data);
         }
@@ -73,6 +91,10 @@ public class OpenApiService : ApplicationService
         {
             return OpenApiEnvelope<OrderParcelCreateOutput>.Fail(ex.Message);
         }
+        catch (JsonException)
+        {
+            return OpenApiEnvelope<OrderParcelCreateOutput>.Fail("请求体格式错误");
+        }
         catch (Exception ex)
         {
             return OpenApiEnvelope<OrderParcelCreateOutput>.Fail(
@@ -80,4 +102,25 @@ public class OpenApiService : ApplicationService
                 "500");
         }
     }
+
+    private async Task<string> ReadRawBodyAsync()
+    {
+        var http = HttpContextAccessor.HttpContext
+            ?? throw new BusinessException("凭证无效");
+        var request = http.Request;
+        request.EnableBuffering();
+        if (request.Body.CanSeek)
+        {
+            request.Body.Position = 0;
+        }
+
+        using var reader = new StreamReader(request.Body, Encoding.UTF8, detectEncodingFromByteOrderMarks: false, leaveOpen: true);
+        var raw = await reader.ReadToEndAsync();
+        if (request.Body.CanSeek)
+        {
+            request.Body.Position = 0;
+        }
+
+        return raw;
+    }
 }
diff --git a/src/Oms.Application/Shared/CustomerOpenApiAuthHelper.cs b/src/Oms.Application/Shared/CustomerOpenApiAuthHelper.cs
index b65658c..0306371 100644
--- a/src/Oms.Application/Shared/CustomerOpenApiAuthHelper.cs
+++ b/src/Oms.Application/Shared/CustomerOpenApiAuthHelper.cs
@@ -10,12 +10,16 @@ using Oms.Domain.CustomersAggregate.Repositories;
 namespace Oms.Application.Shared;
 
 /// <summary>
-/// 客户 OpenAPI 机机鉴权：按请求头 AppKey + AppSecret 解析主客户。
+/// 客户 OpenAPI 机机鉴权：appKey + timestamp + HMAC-SHA256(sign)，Secret 仅本地参与签名。
 /// </summary>
 public class CustomerOpenApiAuthHelper : IScopedDependency
 {
     public const string AppKeyHeaderName = "appKey";
-    public const string AppSecretHeaderName = "appSecret";
+    public const string TimestampHeaderName = "timestamp";
+    public const string SignHeaderName = "sign";
+
+    /// <summary>签名时间窗（秒）。</summary>
+    public const int TimestampSkewSeconds = 300;
 
     private readonly ICustomerOpenApiCredentialRepository _credentialRepository;
     private readonly ICustomerRepository _customerRepository;
@@ -32,38 +36,52 @@ public class CustomerOpenApiAuthHelper : IScopedDependency
     }
 
     /// <summary>
-    /// 从当前请求头读取 appKey / appSecret 并鉴权。
+    /// 校验 Header 签名并解析主客户。
+    /// stringToSign = appKey + "\n" + timestamp + "\n" + sha256Hex(rawBody)
+    /// sign = hex(HMAC-SHA256(appSecret, stringToSign))
     /// </summary>
-    public Task<(Customer Customer, CustomerOpenApiCredential Credential)> ResolveFromHeadersAsync(
-        CancellationToken cancellationToken = default)
-    {
-        var http = _httpContextAccessor.HttpContext
-            ?? throw new BusinessException("凭证无效");
-        var appKey = http.Request.Headers[AppKeyHeaderName].FirstOrDefault();
-        var appSecret = http.Request.Headers[AppSecretHeaderName].FirstOrDefault();
-        return ResolveAsync(appKey, appSecret, cancellationToken);
-    }
-
-    public async Task<(Customer Customer, CustomerOpenApiCredential Credential)> ResolveAsync(
+    public async Task<(Customer Customer, CustomerOpenApiCredential Credential)> ResolveSignedAsync(
         string? appKey,
-        string? appSecret,
+        string? timestamp,
+        string? sign,
+        string? rawBody,
         CancellationToken cancellationToken = default)
     {
         var key = appKey?.Trim();
-        var secret = appSecret?.Trim();
-        if (string.IsNullOrWhiteSpace(key) || string.IsNullOrWhiteSpace(secret))
+        var tsRaw = timestamp?.Trim();
+        var signRaw = sign?.Trim();
+        if (string.IsNullOrWhiteSpace(key)
+            || string.IsNullOrWhiteSpace(tsRaw)
+            || string.IsNullOrWhiteSpace(signRaw))
         {
             throw new BusinessException("凭证无效");
         }
 
+        if (!long.TryParse(tsRaw, out var unixSeconds))
+        {
+            throw new BusinessException("请求已过期");
+        }
+
+        var now = DateTimeOffset.UtcNow.ToUnixTimeSeconds();
+        if (Math.Abs(now - unixSeconds) > TimestampSkewSeconds)
+        {
+            throw new BusinessException("请求已过期");
+        }
+
         var credential = await _credentialRepository.GetByAppKeyAsync(key, cancellationToken);
         if (credential == null
             || !credential.Enabled
-            || !FixedTimeEqualsUtf8(credential.AppSecret, secret))
+            || string.IsNullOrWhiteSpace(credential.AppSecret))
         {
             throw new BusinessException("凭证无效");
         }
 
+        var expectedSign = ComputeSign(key, tsRaw, rawBody ?? string.Empty, credential.AppSecret);
+        if (!FixedTimeEqualsUtf8(expectedSign, signRaw.ToLowerInvariant()))
+        {
+            throw new BusinessException("签名无效");
+        }
+
         var customer = await _customerRepository.FirstOrDefaultAsync(
             x => x.Id == credential.CustomerId,
             cancellationToken);
@@ -81,6 +99,30 @@ public class CustomerOpenApiAuthHelper : IScopedDependency
         return (customer, credential);
     }
 
+    /// <summary>
+    /// 客户端可复用：计算 sign（小写 hex）。
+    /// </summary>
+    public static string ComputeSign(string appKey, string timestamp, string rawBody, string appSecret)
+    {
+        var bodyHash = Sha256Hex(rawBody ?? string.Empty);
+        var stringToSign = $"{appKey}\n{timestamp}\n{bodyHash}";
+        return HmacSha256Hex(appSecret, stringToSign);
+    }
+
+    private static string Sha256Hex(string text)
+    {
+        var bytes = SHA256.HashData(Encoding.UTF8.GetBytes(text));
+        return Convert.ToHexString(bytes).ToLowerInvariant();
+    }
+
+    private static string HmacSha256Hex(string secret, string content)
+    {
+        var keyBytes = Encoding.UTF8.GetBytes(secret);
+        var contentBytes = Encoding.UTF8.GetBytes(content);
+        var hash = HMACSHA256.HashData(keyBytes, contentBytes);
+        return Convert.ToHexString(hash).ToLowerInvariant();
+    }
+
     private static bool FixedTimeEqualsUtf8(string? expected, string actual)
     {
         if (string.IsNullOrEmpty(expected))
diff --git a/src/SimpleAdmin.Api/SimpleAdminApiModule.cs b/src/SimpleAdmin.Api/SimpleAdminApiModule.cs
index 0d0e2a1..b24c7ff 100644
--- a/src/SimpleAdmin.Api/SimpleAdminApiModule.cs
+++ b/src/SimpleAdmin.Api/SimpleAdminApiModule.cs
@@ -167,6 +167,17 @@ public class SimpleAdminApiModule : FakeModule
         // 路由 - 必须在认证和授权之前
         app.UseRouting();
 
+        // OpenAPI 验签需读取原始 Body，允许二次读流
+        app.Use(async (ctx, next) =>
+        {
+            if (ctx.Request.Path.StartsWithSegments("/openapi"))
+            {
+                ctx.Request.EnableBuffering();
+            }
+
+            await next();
+        });
+
         // 认证和授权
         app.UseAuthentication();
         app.UseAuthorization();