diff --git a/backend/app/api/budget.py b/backend/app/api/budget.py
index ad366ae7..1077eef1 100644
--- a/backend/app/api/budget.py
+++ b/backend/app/api/budget.py
@@ -220,7 +220,18 @@ def auto_decompose_budget(
             kpi_version_used[kid] = chosen.version
 
         if not kpi_annual:
-            raise HTTPException(400, "该年度没有可分解的预算，请先在预算执行中录入年度预算")
+            # 查询该企业有哪些年份有年度预算行（供提示）
+            from sqlalchemy import distinct
+            avail_years = [r[0] for r in db.query(distinct(BudgetPlan.budget_year)).filter(
+                BudgetPlan.entity_id == entity_id,
+                BudgetPlan.period.like("%-00"),
+                BudgetPlan.status == "active",
+            ).order_by(BudgetPlan.budget_year).all()]
+            hint = f"该年度({year})没有年度预算总额（period=YYYY-00）"
+            if avail_years:
+                hint += f"；现有年度数据年份：{', '.join(str(y) for y in avail_years)}"
+            hint += "。请先在预算录入中填写该年度预算总额，或改用战略预算编制按地图录入；如需按已有月度数据反向生成请咨询管理员。"
+            raise HTTPException(400, hint)
 
         results = []
         created_count = 0
@@ -293,7 +304,7 @@ def auto_decompose_budget(
 
     # ── 单KPI模式（原有逻辑）──
     if annual_budget is None:
-        raise HTTPException(400, "缺少必要参数: annual_budget")
+        raise HTTPException(400, "缺少必要参数: annual_budget（单KPI分解需传年度预算值）")
 
     kpi = db.query(KPIDefinition).filter(KPIDefinition.id == kpi_id).first()
     if not kpi: