diff --git a/app/demo_account.py b/app/demo_account.py
index 9661b8a..f6e70b4 100644
--- a/app/demo_account.py
+++ b/app/demo_account.py
@@ -1,8 +1,13 @@
-from datetime import datetime, timezone
-from pydantic import BaseModel, Field
+from datetime import datetime
+from pydantic import BaseModel, ConfigDict, Field
+from sqlalchemy.orm import Session
+
+from app.models import DemoAccountState, DemoTradeRecord
 
 
 class DemoTrade(BaseModel):
+    model_config = ConfigDict(from_attributes=True)
+
     id: int
     market: str
     side: str
@@ -10,7 +15,7 @@ class DemoTrade(BaseModel):
     amount: float
     quote_amount: float
     reason: str
-    created_at: datetime = Field(default_factory=lambda: datetime.now(timezone.utc))
+    created_at: datetime
 
 
 class DemoAccount(BaseModel):
@@ -25,24 +30,46 @@ class DemoAccountService:
     def __init__(self, initial_balance: float, quote_asset: str) -> None:
         self.initial_balance = initial_balance
         self.quote_asset = quote_asset
-        self.account = DemoAccount(
-            quote_asset=quote_asset,
-            balance=initial_balance,
-            equity=initial_balance,
+
+    def _get_or_create_state(self, db: Session) -> DemoAccountState:
+        state = db.get(DemoAccountState, 1)
+        if state is None:
+            state = DemoAccountState(
+                id=1,
+                quote_asset=self.quote_asset,
+                balance=self.initial_balance,
+                equity=self.initial_balance,
+                realized_pnl=0.0,
+            )
+            db.add(state)
+            db.commit()
+            db.refresh(state)
+        return state
+
+    def snapshot(self, db: Session) -> DemoAccount:
+        state = self._get_or_create_state(db)
+        trades = db.query(DemoTradeRecord).order_by(DemoTradeRecord.id.desc()).limit(100).all()
+        return DemoAccount(
+            quote_asset=state.quote_asset,
+            balance=state.balance,
+            equity=state.equity,
+            realized_pnl=state.realized_pnl,
+            trades=[DemoTrade.model_validate(trade) for trade in reversed(trades)],
         )
 
-    def snapshot(self) -> DemoAccount:
-        return self.account
+    def reset(self, db: Session) -> DemoAccount:
+        db.query(DemoTradeRecord).delete()
+        state = self._get_or_create_state(db)
+        state.quote_asset = self.quote_asset
+        state.balance = self.initial_balance
+        state.equity = self.initial_balance
+        state.realized_pnl = 0.0
+        db.add(state)
+        db.commit()
+        db.refresh(state)
+        return self.snapshot(db)
 
-    def reset(self) -> DemoAccount:
-        self.account = DemoAccount(
-            quote_asset=self.quote_asset,
-            balance=self.initial_balance,
-            equity=self.initial_balance,
-        )
-        return self.account
-
-    def add_demo_trade(self, market: str, side: str, price: float, amount: float, reason: str) -> DemoTrade:
+    def add_demo_trade(self, db: Session, market: str, side: str, price: float, amount: float, reason: str) -> DemoTrade:
         if price <= 0 or amount <= 0:
             raise ValueError('price and amount must be positive')
 
@@ -51,17 +78,18 @@ class DemoAccountService:
         if side_normalized not in {'buy', 'sell'}:
             raise ValueError('side must be buy or sell')
 
-        if side_normalized == 'buy':
-            if quote_amount > self.account.balance:
-                raise ValueError('not enough demo balance')
-            self.account.balance -= quote_amount
-        else:
-            self.account.balance += quote_amount
-            self.account.realized_pnl += quote_amount
+        state = self._get_or_create_state(db)
 
-        self.account.equity = self.account.balance
-        trade = DemoTrade(
-            id=len(self.account.trades) + 1,
+        if side_normalized == 'buy':
+            if quote_amount > state.balance:
+                raise ValueError('not enough demo balance')
+            state.balance -= quote_amount
+        else:
+            state.balance += quote_amount
+            state.realized_pnl += quote_amount
+
+        state.equity = state.balance
+        trade = DemoTradeRecord(
             market=market.upper(),
             side=side_normalized,
             price=price,
@@ -69,5 +97,8 @@ class DemoAccountService:
             quote_amount=quote_amount,
             reason=reason,
         )
-        self.account.trades.append(trade)
-        return trade
+        db.add(state)
+        db.add(trade)
+        db.commit()
+        db.refresh(trade)
+        return DemoTrade.model_validate(trade)