diff --git a/lib/strategy/templates/trade_policy_fields.html b/lib/strategy/templates/trade_policy_fields.html
index 137f1d9..449c1ec 100644
--- a/lib/strategy/templates/trade_policy_fields.html
+++ b/lib/strategy/templates/trade_policy_fields.html
@@ -4,10 +4,13 @@
 {% endif %}
 {% macro trade_policy_symbol(name, id, value='', required=true, placeholder='BTC 或 BTC/USDT') -%}
 {% if trade_policy.symbol_restrict_enabled and trade_policy.symbol_whitelist %}
-<select name="{{ name }}" id="{{ id }}" {% if required %}required{% endif %} class="trade-policy-symbol-select">
-    <option value="">选择币种</option>
-    {% for sym in trade_policy.symbol_whitelist %}
-    <option value="{{ sym }}" {% if value and ((value|upper) == sym or (value|upper).startswith(sym ~ '/')) %}selected{% endif %}>{{ sym }}/USDT</option>
+{% set wl = trade_policy.symbol_whitelist %}
+{% set sole_sym = wl[0] if (wl|length) == 1 else '' %}
+{% set effective = value if value else sole_sym %}
+<select name="{{ name }}" id="{{ id }}" {% if required %}required{% endif %} class="trade-policy-symbol-select"{% if sole_sym %} data-sole-symbol="{{ sole_sym }}"{% endif %}>
+    {% if not sole_sym %}<option value="">选择币种</option>{% endif %}
+    {% for sym in wl %}
+    <option value="{{ sym }}" {% if effective and ((effective|upper) == sym or (effective|upper).startswith(sym ~ '/')) %}selected{% endif %}>{{ sym }}/USDT</option>
     {% endfor %}
 </select>
 {% else %}
diff --git a/lib/trade/trade_policy_app_lib.py b/lib/trade/trade_policy_app_lib.py
index 3d7adf2..b35ea3f 100644
--- a/lib/trade/trade_policy_app_lib.py
+++ b/lib/trade/trade_policy_app_lib.py
@@ -17,15 +17,20 @@ def trade_policy_template_context(policy: TradePolicy) -> dict:
 
 
 def default_symbol_for_policy(policy: TradePolicy, raw_default: str) -> str:
-    d = (raw_default or "BTC/USDT").strip() or "BTC/USDT"
+    d = (raw_default or "").strip()
     if policy.symbol_restrict_enabled and policy.symbol_whitelist:
+        # 白名单仅一币时直接用 env 币种,表单下拉同步默认选中
+        if len(policy.symbol_whitelist) == 1:
+            return f"{policy.symbol_whitelist[0]}/USDT"
         from lib.trade.trade_policy_lib import symbol_base_coin
 
-        base = symbol_base_coin(d)
+        base = symbol_base_coin(d or "BTC/USDT")
         if base not in policy.symbol_whitelist:
             return f"{policy.symbol_whitelist[0]}/USDT"
-    return d
-
+        if d:
+            return d if "/" in d else f"{base}/USDT"
+        return f"{policy.symbol_whitelist[0]}/USDT"
+    return d or "BTC/USDT"
 
 def check_symbol_policy(
     policy: TradePolicy,
diff --git a/tests/test_trade_policy_lib.py b/tests/test_trade_policy_lib.py
index 617c980..2e9d152 100644
--- a/tests/test_trade_policy_lib.py
+++ b/tests/test_trade_policy_lib.py
@@ -88,3 +88,29 @@ def test_badge_parts():
         }
     )
     assert trade_policy_badge_parts(p) == ("仅多", "BTC/ETH")
+
+
+def test_default_symbol_when_whitelist_sole():
+    from lib.trade.trade_policy_app_lib import default_symbol_for_policy
+
+    p = load_trade_policy(
+        {
+            "TRADE_SYMBOL_RESTRICT_ENABLED": "true",
+            "TRADE_SYMBOL_WHITELIST": "BTC",
+        }
+    )
+    assert default_symbol_for_policy(p, "") == "BTC/USDT"
+    assert default_symbol_for_policy(p, "ETH/USDT") == "BTC/USDT"
+
+
+def test_default_symbol_when_whitelist_multi():
+    from lib.trade.trade_policy_app_lib import default_symbol_for_policy
+
+    p = load_trade_policy(
+        {
+            "TRADE_SYMBOL_RESTRICT_ENABLED": "true",
+            "TRADE_SYMBOL_WHITELIST": "BTC,ETH",
+        }
+    )
+    assert default_symbol_for_policy(p, "ETH") == "ETH/USDT"
+    assert default_symbol_for_policy(p, "SOL/USDT") == "BTC/USDT"