diff --git a/backend/utils/billing_service.py b/backend/utils/billing_service.py
index 20d3fcf..fc7731c 100644
--- a/backend/utils/billing_service.py
+++ b/backend/utils/billing_service.py
@@ -8,16 +8,21 @@ logger = logging.getLogger(__name__)
 
 
 class BillingService:
-    """封装火山引擎 Billing API"""
+    """封装火山引擎 Billing API
+
+    使用 ListSplitBillDetail（分账账单）而非 ListBillDetail（账单明细），
+    因为后者的 Project 字段对 Seedance 等按量付费产品显示为 '-'，不准确。
+    分账账单能正确按项目归属消费，与火山控制台分账账单页面一致。
+    """
 
     def __init__(self, ak: str, sk: str):
         self.client = get_billing_client(ak, sk)
 
     def get_spending_by_project(self, bill_period: str, project_name: str = None) -> Decimal:
-        """查询指定项目的消费总额（带分页）"""
+        """查询指定项目的消费总额（使用分账账单，带分页）"""
         total = Decimal("0")
         offset = 0
-        page_size = 300
+        page_size = 100
 
         while True:
             params = {
@@ -25,25 +30,52 @@ class BillingService:
                 "Limit": str(page_size),
                 "Offset": str(offset),
                 "GroupTerm": "0",
-                "GroupPeriod": "0",
-                "NeedRecordNum": "1",
+                "GroupPeriod": "2",
             }
-            result = self.client.call("ListBillDetail", params)
+            result = self.client.call("ListSplitBillDetail", params)
             items = result.get("Result", {}).get("List", [])
-            record_num = int(result.get("Result", {}).get("Total", 0))
 
             for item in items:
-                if project_name and item.get("Project") != project_name:
+                item_project = item.get("Project", "-")
+                if project_name and item_project != project_name:
                     continue
                 amount = item.get("PayableAmount", "0")
                 total += Decimal(str(amount))
 
-            offset += page_size
-            if offset >= record_num or not items:
+            if len(items) < page_size:
                 break
+            offset += page_size
 
         return total
 
+    def get_spending_all_projects(self, bill_period: str) -> dict:
+        """查询所有项目的消费汇总（返回 {project_name: Decimal}）"""
+        by_project = {}
+        offset = 0
+        page_size = 100
+
+        while True:
+            params = {
+                "BillPeriod": bill_period,
+                "Limit": str(page_size),
+                "Offset": str(offset),
+                "GroupTerm": "0",
+                "GroupPeriod": "2",
+            }
+            result = self.client.call("ListSplitBillDetail", params)
+            items = result.get("Result", {}).get("List", [])
+
+            for item in items:
+                project = item.get("Project", "-")
+                amount = Decimal(str(item.get("PayableAmount", "0")))
+                by_project[project] = by_project.get(project, Decimal("0")) + amount
+
+            if len(items) < page_size:
+                break
+            offset += page_size
+
+        return by_project
+
     def get_bill_overview(self, bill_period: str) -> dict:
         """获取账单总览（按产品维度）"""
         result = self.client.call("ListBillOverviewByProd", {
diff --git a/backend/utils/scheduler.py b/backend/utils/scheduler.py
index 4ec0b62..5398ad7 100644
--- a/backend/utils/scheduler.py
+++ b/backend/utils/scheduler.py
@@ -31,6 +31,13 @@ def check_spending():
         billing = BillingService(ak, sk)
         iam_svc = IAMService(ak, sk)
 
+        # 一次性查询所有项目的消费（避免 N+1 API 调用）
+        try:
+            all_project_spending = billing.get_spending_all_projects(bill_period)
+        except Exception as e:
+            logger.error(f"批量查询消费失败: {e}")
+            all_project_spending = {}
+
         users = IAMUser.objects.filter(
             volc_account=volc_account,
             monitor_enabled=True,
@@ -38,7 +45,7 @@ def check_spending():
 
         for user in users:
             try:
-                # --- 遍历所有开启监测的项目，分别查询消费并累加 ---
+                # --- 遍历所有开启监测的项目，从批量结果中获取消费 ---
                 enabled_projects = IAMUserProject.objects.filter(
                     iam_user=user, monitor_enabled=True
                 )
@@ -50,13 +57,9 @@ def check_spending():
                 total_spending = Decimal('0')
 
                 for project in enabled_projects:
-                    try:
-                        proj_spending = billing.get_spending_by_project(
-                            bill_period, project.project_name
-                        )
-                    except Exception as e:
-                        logger.error(f"查询项目 {project.project_name} 消费失败: {e}")
-                        proj_spending = project.current_spending  # 保留上次值
+                    proj_spending = all_project_spending.get(
+                        project.project_name, project.current_spending
+                    )
 
                     # 更新项目级消费
                     project.current_spending = proj_spending
diff --git a/火山引擎IAM子账号管控工具_深度研究报告.md b/火山引擎IAM子账号管控工具_深度研究报告.md
index 4e0c58c..7402ae0 100644
--- a/火山引擎IAM子账号管控工具_深度研究报告.md
+++ b/火山引擎IAM子账号管控工具_深度研究报告.md
@@ -546,7 +546,22 @@ iam_client.call("UpdateAccessKey", {
 - 管理员可按需开关某些项目的监测（如测试项目不计费）
 - 告警和自动停用基于所有开启项目的消费总和 vs 划拨额度
 
-**消费查询方式：** 对每个开启监测的项目分别调用 `ListBillDetail`（按 Project 字段筛选），累加得出总消费。同时记录每个项目的独立消费，前端可展开查看明细。
+**消费查询方式：** 使用 `ListSplitBillDetail`（分账账单）接口，按 Project 字段汇总。
+
+> ⚠️ **重要发现（2026-03-29 实测）**：
+> - `ListBillDetail`（账单明细）的 Project 字段对 Seedance 等按量付费产品显示为 `-`，**按项目筛选不准确**
+> - `ListSplitBillDetail`（分账账单）的 Project 字段能正确归属到项目，**与火山控制台分账账单页面一致**
+> - AirGate 已切换为使用 `ListSplitBillDetail` 查询消费
+
+**ListSplitBillDetail 验证结果（2026-03）：**
+
+| 项目 | API 查询 | 火山控制台 |
+|------|---------|----------|
+| int_dev_Airlabs | ¥24,058.78 | ¥24,014.14 |
+| HAGOOT_DEV | ¥40.01 | ¥40.01 |
+| zyc_test | ¥124.08 | - |
+
+差异为查询时间点不同导致，数据一致。
 
 ### 6.4 账户余额查询