diff --git a/backend/src/routes/payroll.routes.ts b/backend/src/routes/payroll.routes.ts
index 49f8799..1a24138 100644
--- a/backend/src/routes/payroll.routes.ts
+++ b/backend/src/routes/payroll.routes.ts
@@ -596,8 +596,8 @@ router.post('/tax-preview', async (req: AuthRequest, res: Response, next: NextFu
     ])
 
     const emp = employee || { socialInsBase: baseSalary, housingFundBase: baseSalary }
-    const socialBase = emp.socialInsBase || baseSalary
-    const housingBase = emp.housingFundBase || baseSalary
+    const socialBase = emp.socialInsBase != null ? emp.socialInsBase : baseSalary
+    const housingBase = emp.housingFundBase != null ? emp.housingFundBase : baseSalary
 
     // 计算社保公积金
     let socialEmp = 0, housingEmp = 0
diff --git a/backend/src/services/payroll.service.ts b/backend/src/services/payroll.service.ts
index a1c384c..698359f 100644
--- a/backend/src/services/payroll.service.ts
+++ b/backend/src/services/payroll.service.ts
@@ -233,9 +233,9 @@ export async function calcBatchEntry(
     })
   }
 
-  // 社保基数：优先用员工核定基数，否则用基本工资
-  const socialBase = employee.socialInsBase || inputs.baseSalary
-  const housingBase = employee.housingFundBase || inputs.baseSalary
+  // 社保基数：优先用员工核定基数（含0，劳务协议人员基数为0不交社保），未设置时回退到基本工资
+  const socialBase = employee.socialInsBase != null ? employee.socialInsBase : inputs.baseSalary
+  const housingBase = employee.housingFundBase != null ? employee.housingFundBase : inputs.baseSalary
 
   let socialEmp = 0, socialOrg = 0, housingEmp = 0, housingOrg = 0
 
@@ -689,7 +689,7 @@ export async function prePayrollCheck(orgId: string, batchId: string): Promise<P
   // 1. 社保基数是否在上下限范围内
   if (socialConfig) {
     for (const entry of entries) {
-      const base = entry.employee.socialInsBase || entry.baseSalary
+      const base = entry.employee.socialInsBase != null ? entry.employee.socialInsBase : entry.baseSalary
       if (base < socialConfig.baseMin || base > socialConfig.baseMax) {
         checks.push({
           code: 'SOCIAL_BASE_OUT_OF_RANGE',
@@ -707,7 +707,7 @@ export async function prePayrollCheck(orgId: string, batchId: string): Promise<P
   // 2. 公积金基数是否在上下限范围内
   if (housingConfig) {
     for (const entry of entries) {
-      const base = entry.employee.housingFundBase || entry.baseSalary
+      const base = entry.employee.housingFundBase != null ? entry.employee.housingFundBase : entry.baseSalary
       if (base < housingConfig.baseMin || base > housingConfig.baseMax) {
         checks.push({
           code: 'HOUSING_BASE_OUT_OF_RANGE',