diff --git a/backend/src/main/java/com/xly/erp/module/mod/service/impl/ModuleServiceImpl.java b/backend/src/main/java/com/xly/erp/module/mod/service/impl/ModuleServiceImpl.java
index 28a8c35..b331c6b 100644
--- a/backend/src/main/java/com/xly/erp/module/mod/service/impl/ModuleServiceImpl.java
+++ b/backend/src/main/java/com/xly/erp/module/mod/service/impl/ModuleServiceImpl.java
@@ -146,19 +146,20 @@ public class ModuleServiceImpl implements ModuleService {
             throw new BizException(ErrorCode.MOD_HAS_REFERENCES);
         }
 
-        // 3. 软删除写入：仅触碰三件套，避免覆盖其他字段；并以 bDeleted=0 兜底并发
-        ModuleEntity patch = new ModuleEntity();
-        patch.setIIncrement(id);
-        patch.setBDeleted(true);
-        patch.setTDeletedDate(LocalDateTime.now());
-        // sDeletedBy 留 null（FieldStrategy 默认 NOT_NULL 跳过；REQ-USR-004 后由登录上下文回填）
-
-        int affected = moduleMapper.update(patch,
-                new LambdaUpdateWrapper<ModuleEntity>()
-                        .eq(ModuleEntity::getIIncrement, id)
-                        .eq(ModuleEntity::getBDeleted, false));
+        // 3. 软删除写入：用 LambdaUpdateWrapper.set 显式声明 SET 列，避免 entity 驱动 SET
+        //    （iParentId 字段的 FieldStrategy.IGNORED 策略会让 entity-driven update 把
+        //     iParentId 写成 NULL，破坏父引用——这里用 wrapper.set 完全绕开 entity）
+        //    sDeletedBy 暂写 null（REQ-USR-004 后由登录上下文回填）。
+        //    eq(bDeleted, false) 兜底并发：影响 0 行视为已被并发删除 → 40421
+        LambdaUpdateWrapper<ModuleEntity> uw = new LambdaUpdateWrapper<ModuleEntity>()
+                .eq(ModuleEntity::getIIncrement, id)
+                .eq(ModuleEntity::getBDeleted, false)
+                .set(ModuleEntity::getBDeleted, true)
+                .set(ModuleEntity::getTDeletedDate, LocalDateTime.now())
+                .set(ModuleEntity::getSDeletedBy, null);
+
+        int affected = moduleMapper.update(null, uw);
         if (affected == 0) {
-            // 校验后被并发删除
             throw new BizException(ErrorCode.MOD_NOT_FOUND);
         }
 
diff --git a/backend/src/test/java/com/xly/erp/module/mod/controller/ModuleControllerIT.java b/backend/src/test/java/com/xly/erp/module/mod/controller/ModuleControllerIT.java
index ca53dda..159146d 100644
--- a/backend/src/test/java/com/xly/erp/module/mod/controller/ModuleControllerIT.java
+++ b/backend/src/test/java/com/xly/erp/module/mod/controller/ModuleControllerIT.java
@@ -340,6 +340,47 @@ class ModuleControllerIT {
     }
 
     @Test
+    void delete_preservesOtherFields_onChildModule() throws Exception {
+        // 反例：非 root 子模块软删除后，iParentId / sProcedureName / sModuleNameZh /
+        // iSortOrder 等字段必须保持原值（spec § 业务规则 #4 + 验收 #1）。
+        Integer parentId = insertExisting("sp_del_pres_p_" + System.nanoTime(), null);
+        String childProc = "sp_del_pres_c_" + System.nanoTime();
+        // 用自定义字段值的 child（与 insertExisting 默认值不同），便于事后比对
+        ModuleEntity child = new ModuleEntity();
+        child.setSDisplayType("接口");
+        child.setSProcedureName(childProc);
+        child.setSModuleType("AUDIT");
+        child.setSManageDeptEn("OPS");
+        child.setBShowPermission(true);
+        child.setSModuleNameZh("待保留中文名");
+        child.setIParentId(parentId);
+        child.setISortOrder(7);
+        child.setBDeleted(false);
+        child.setTCreateDate(LocalDateTime.now());
+        moduleMapper.insert(child);
+        Integer childId = child.getIIncrement();
+
+        mockMvc.perform(delete("/api/modules/" + childId))
+                .andExpect(status().isOk())
+                .andExpect(jsonPath("$.code").value(200))
+                .andExpect(jsonPath("$.data.bDeleted").value(true));
+
+        ModuleEntity reloaded = moduleMapper.selectById(childId);
+        // 软删除三件套生效
+        assertThat(reloaded.getBDeleted()).isTrue();
+        assertThat(reloaded.getTDeletedDate()).isNotNull();
+        // 关键：其他列保持原值（曾经 iParentId.FieldStrategy.IGNORED 会清零这一列，本断言钉死该回归）
+        assertThat(reloaded.getIParentId()).isEqualTo(parentId);
+        assertThat(reloaded.getSProcedureName()).isEqualTo(childProc);
+        assertThat(reloaded.getSDisplayType()).isEqualTo("接口");
+        assertThat(reloaded.getSModuleType()).isEqualTo("AUDIT");
+        assertThat(reloaded.getSManageDeptEn()).isEqualTo("OPS");
+        assertThat(reloaded.getBShowPermission()).isTrue();
+        assertThat(reloaded.getSModuleNameZh()).isEqualTo("待保留中文名");
+        assertThat(reloaded.getISortOrder()).isEqualTo(7);
+    }
+
+    @Test
     void delete_responseVOContainsOnlyIIncrementAndBDeleted() throws Exception {
         Integer id = insertExisting("sp_del_vo_" + System.nanoTime(), null);
 
diff --git a/backend/src/test/java/com/xly/erp/module/mod/service/ModuleServiceImplTest.java b/backend/src/test/java/com/xly/erp/module/mod/service/ModuleServiceImplTest.java
index 3179596..9b5f005 100644
--- a/backend/src/test/java/com/xly/erp/module/mod/service/ModuleServiceImplTest.java
+++ b/backend/src/test/java/com/xly/erp/module/mod/service/ModuleServiceImplTest.java
@@ -24,6 +24,7 @@ import java.time.LocalDateTime;
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatThrownBy;
 import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.isNull;
 import static org.mockito.Mockito.never;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.when;
@@ -360,13 +361,9 @@ class ModuleServiceImplTest {
 
         assertThat(vo.getIIncrement()).isEqualTo(23);
         assertThat(vo.getBDeleted()).isTrue();
-
-        ArgumentCaptor<ModuleEntity> cap = ArgumentCaptor.forClass(ModuleEntity.class);
-        verify(moduleMapper).update(cap.capture(), (Wrapper<ModuleEntity>) any());
-        ModuleEntity patch = cap.getValue();
-        assertThat(patch.getIIncrement()).isEqualTo(23);
-        assertThat(patch.getBDeleted()).isTrue();
-        assertThat(patch.getTDeletedDate()).isNotNull();
+        // SET 列由 LambdaUpdateWrapper 声明，entity 第一参数为 null（避免 iParentId.IGNORED 策略副作用）
+        // 实际 SQL SET 子句的列覆盖由 IT (delete_preservesOtherFields_onChildModule) 验证
+        verify(moduleMapper).update((ModuleEntity) isNull(), (Wrapper<ModuleEntity>) any());
     }
 
     @Test