diff --git a/backend/app/services/market_overview_builder.py b/backend/app/services/market_overview_builder.py
index f879fb4..9f65931 100644
--- a/backend/app/services/market_overview_builder.py
+++ b/backend/app/services/market_overview_builder.py
@@ -237,6 +237,16 @@ def _symbol_keys(row: dict, config: ExtConfig) -> list[str]:
     return keys
 
 
+def _leader_sort_key(row: dict) -> float:
+    """领涨股排序键: 缺涨跌幅的成分股排最后。
+
+    0.00% 是有效涨跌幅, 不能与"无行情"合并成同一个哨兵值 —— 板块整体下跌时
+    平盘股就是领涨股。
+    """
+    value = _finite(row.get("change_pct"))
+    return value if value is not None else float("-inf")
+
+
 def _dimension_rank(rows: list[dict], repo, kind: str, limit: int = 5, level: int | None = None) -> dict:
     if not rows:
         return {"leading": [], "lagging": []}
@@ -281,7 +291,7 @@ def _dimension_rank(rows: list[dict], repo, kind: str, limit: int = 5, level: in
         changes = [v for v in changes if v is not None]
         if not changes:
             continue
-        leader = max(stocks, key=lambda s: _finite(s.get("change_pct")) or -999)
+        leader = max(stocks, key=_leader_sort_key)
         items.append({
             "name": name,
             "count": len(stocks),
diff --git a/backend/tests/test_overview_dimension_leader.py b/backend/tests/test_overview_dimension_leader.py
new file mode 100644
index 0000000..004b4ef
--- /dev/null
+++ b/backend/tests/test_overview_dimension_leader.py
@@ -0,0 +1,89 @@
+"""市场总览「领涨股」选取: 涨跌幅 0.00% 是有效值, 不能被当成缺失值。"""
+from __future__ import annotations
+
+import json
+
+import polars as pl
+
+from app.services.market_overview_builder import _dimension_rank
+
+
+def _fake_repo(tmp_path):
+    import types
+
+    return types.SimpleNamespace(store=types.SimpleNamespace(data_dir=tmp_path))
+
+
+def _write_concept_ext(tmp_path, mapping: dict[str, str]) -> None:
+    """写一张 snapshot 模式的概念扩展表 (symbol → 所属概念)。"""
+    cfg_dir = tmp_path / "ext_data" / "concept_tbl"
+    cfg_dir.mkdir(parents=True, exist_ok=True)
+    cfg_dir.joinpath("config.json").write_text(
+        json.dumps({
+            "id": "concept_tbl",
+            "label": "概念表",
+            "mode": "snapshot",
+            "fields": [{"name": "所属概念", "dtype": "string", "label": "所属概念"}],
+        }, ensure_ascii=False),
+        encoding="utf-8",
+    )
+    pl.DataFrame({
+        "symbol": list(mapping.keys()),
+        "所属概念": list(mapping.values()),
+    }).write_parquet(cfg_dir / "part.parquet")
+
+
+def test_flat_stock_can_be_leader_of_a_falling_concept(tmp_path):
+    """全概念下跌、最强的一只恰好平盘(0.00%)时, 领涨股必须是那只平盘股。"""
+    _write_concept_ext(tmp_path, {
+        "000001.SZ": "人工智能",
+        "000002.SZ": "人工智能",
+        "000003.SZ": "人工智能",
+    })
+    rows = [
+        {"symbol": "000001.SZ", "name": "跌一", "change_pct": -0.01, "amount": 1e8},
+        {"symbol": "000002.SZ", "name": "平盘", "change_pct": 0.0, "amount": 2e8},
+        {"symbol": "000003.SZ", "name": "跌三", "change_pct": -0.03, "amount": 3e8},
+    ]
+
+    result = _dimension_rank(rows, _fake_repo(tmp_path), "concept")
+
+    items = {item["name"]: item for item in result["lagging"]}
+    assert "人工智能" in items
+    leader = items["人工智能"]["leader"]
+    assert leader["name"] == "平盘"
+    assert leader["change_pct"] == 0.0
+
+
+def test_leader_falls_back_to_none_pct_last(tmp_path):
+    """change_pct 缺失(None)的成分股仍排在所有有值的成分股之后。"""
+    _write_concept_ext(tmp_path, {
+        "000001.SZ": "芯片",
+        "000002.SZ": "芯片",
+    })
+    rows = [
+        {"symbol": "000001.SZ", "name": "无行情", "change_pct": None, "amount": 1e8},
+        {"symbol": "000002.SZ", "name": "微跌", "change_pct": -0.02, "amount": 1e8},
+    ]
+
+    result = _dimension_rank(rows, _fake_repo(tmp_path), "concept")
+
+    items = {item["name"]: item for item in result["lagging"]}
+    assert items["芯片"]["leader"]["name"] == "微跌"
+
+
+def test_leader_still_picks_max_when_all_positive(tmp_path):
+    """普通情形不受影响: 全部上涨时仍取涨幅最大的一只。"""
+    _write_concept_ext(tmp_path, {
+        "000001.SZ": "光伏",
+        "000002.SZ": "光伏",
+    })
+    rows = [
+        {"symbol": "000001.SZ", "name": "涨多", "change_pct": 0.05, "amount": 1e8},
+        {"symbol": "000002.SZ", "name": "涨少", "change_pct": 0.01, "amount": 1e8},
+    ]
+
+    result = _dimension_rank(rows, _fake_repo(tmp_path), "concept")
+
+    items = {item["name"]: item for item in result["leading"]}
+    assert items["光伏"]["leader"]["name"] == "涨多"