diff --git a/src/InterfaceForward.Application/Services/Interface/InterfaceService.cs b/src/InterfaceForward.Application/Services/Interface/InterfaceService.cs
index e8ad644..9256f66 100644
--- a/src/InterfaceForward.Application/Services/Interface/InterfaceService.cs
+++ b/src/InterfaceForward.Application/Services/Interface/InterfaceService.cs
@@ -273,15 +273,12 @@ public class InterfaceService : ApplicationService
         var entity = await ServiceProviderRepository.GetFirstAsync(x => x.Id == serviceProviderId);
         if (entity == null) throw new BusinessException("服务商不存在，系统接口自己定义code谢谢配合");
 
-        string res = entity.Code;
+        // 取末三位序号最大值，不能按 Id 取最后一条（删除/手工建码会导致 Id 与序号不一致）
+        var maxSequence = await InterfaceRepository.GetMaxCodeSequenceBySpId(serviceProviderId);
+        if (maxSequence >= 999)
+            throw new BusinessException("该服务商接口代码已达上限（999）");
 
-        // tips：要考虑并发
-        var code = await InterfaceRepository.GetCurrentCodeBySpId(serviceProviderId);
-        int count = 0;
-        if (!string.IsNullOrEmpty(code)) count = int.Parse(code.Substring(code.Length - 3, 3));
-        res += (count + 1).ToString().PadLeft(3, '0');
-
-        return res;
+        return entity.Code + (maxSequence + 1).ToString().PadLeft(3, '0');
     }
 
     private async Task UpdateInterfaceAsync(SaveInterfaceInput input)
diff --git a/src/InterfaceForward.Repositories/Interface/Services/IInterfaceRepository.cs b/src/InterfaceForward.Repositories/Interface/Services/IInterfaceRepository.cs
index 76e0823..14ab411 100644
--- a/src/InterfaceForward.Repositories/Interface/Services/IInterfaceRepository.cs
+++ b/src/InterfaceForward.Repositories/Interface/Services/IInterfaceRepository.cs
@@ -27,11 +27,11 @@ namespace InterfaceForward.Repositories.Interface.Services
         Task<List<InterfaceParameterOutputValueObject>> GetParameterListByIdAsync(int id, bool onlyLeafs = false);
 
         /// <summary>
-        /// 获取服务商接口当前用到的code
+        /// 获取服务商下游接口 code 末三位序号的最大值（含软删，避免复用已占用序号）
         /// </summary>
         /// <param name="spId"></param>
-        /// /// <returns></returns>
-        Task<string> GetCurrentCodeBySpId(int spId);
+        /// <returns>无记录时返回 0</returns>
+        Task<int> GetMaxCodeSequenceBySpId(int spId);
 
         Task<PagedResult<InterfacePaginatedOutputValueObject>> GetInterfacePaginatedListAsync(InterfacePaginatedInputObjectValue input);
     }
diff --git a/src/InterfaceForward.Repositories/Interface/Services/InterfaceRepository.cs b/src/InterfaceForward.Repositories/Interface/Services/InterfaceRepository.cs
index c5cd256..363bd95 100644
--- a/src/InterfaceForward.Repositories/Interface/Services/InterfaceRepository.cs
+++ b/src/InterfaceForward.Repositories/Interface/Services/InterfaceRepository.cs
@@ -68,16 +68,25 @@ public class InterfaceRepository : BasicRepository<InterfaceEntity>, IInterfaceR
     }
 
     /// <inheritdoc />
-    public async Task<string> GetCurrentCodeBySpId(int spId)
+    public async Task<int> GetMaxCodeSequenceBySpId(int spId)
     {
-        var code = await AsQueryable()
+        var codes = await AsQueryable()
             .Where(x => x.ServiceProviderId == spId && !x.IsUpStream)
             .Filter(null, true)
-            .OrderByDescending(x => x.Id)
             .Select(x => x.Code)
-            .FirstAsync();
+            .ToListAsync();
 
-        return code;
+        var max = 0;
+        foreach (var code in codes)
+        {
+            if (string.IsNullOrEmpty(code) || code.Length < 3)
+                continue;
+
+            if (int.TryParse(code.AsSpan(code.Length - 3, 3), out var sequence) && sequence > max)
+                max = sequence;
+        }
+
+        return max;
     }
 
     /// <inheritdoc />