diff --git a/contracts/DODOPrivatePool/impl/DPPTrader.sol b/contracts/DODOPrivatePool/impl/DPPTrader.sol
index ba64c4d..3e3ac0e 100644
--- a/contracts/DODOPrivatePool/impl/DPPTrader.sol
+++ b/contracts/DODOPrivatePool/impl/DPPTrader.sol
@@ -25,7 +25,10 @@ contract DPPTrader is DPPVault {
     }
 
     modifier isSellAllow(address trader) {
-        require(!_SELLING_CLOSE_ && _TRADE_PERMISSION_.isAllowed(trader),"TRADER_SELL_NOT_ALLOWED");
+        require(
+            !_SELLING_CLOSE_ && _TRADE_PERMISSION_.isAllowed(trader),
+            "TRADER_SELL_NOT_ALLOWED"
+        );
         _;
     }
 
@@ -75,7 +78,10 @@ contract DPPTrader is DPPVault {
         uint256 newQuoteTarget;
 
         PMMPricing.RState newRState;
-        (receiveBaseAmount, mtFee, newRState, newQuoteTarget) = querySellQuote(tx.origin,quoteInput);
+        (receiveBaseAmount, mtFee, newRState, newQuoteTarget) = querySellQuote(
+            tx.origin,
+            quoteInput
+        );
 
         _transferBaseOut(to, receiveBaseAmount);
         _transferBaseOut(_MAINTAINER_, mtFee);
@@ -105,15 +111,15 @@ contract DPPTrader is DPPVault {
         uint256 baseBalance = _BASE_TOKEN_.balanceOf(address(this));
         uint256 quoteBalance = _QUOTE_TOKEN_.balanceOf(address(this));
 
-        // no output -> pure profit
-        if (baseBalance >= _BASE_RESERVE_ && quoteBalance >= _QUOTE_RESERVE_) return;
-
         // no input -> pure loss
         require(
             baseBalance >= _BASE_RESERVE_ || quoteBalance >= _QUOTE_RESERVE_,
             "FLASH_LOAN_FAILED"
         );
 
+        // no output -> pure profit
+        if (baseBalance >= _BASE_RESERVE_ && quoteBalance >= _QUOTE_RESERVE_) return;
+
         // sell quote case
         // quote input + base output
         if (baseBalance < _BASE_RESERVE_) {
@@ -223,4 +229,9 @@ contract DPPTrader is DPPVault {
     function getMidPrice() public view returns (uint256 midPrice) {
         return PMMPricing.getMidPrice(getPMMState());
     }
+
+    function _syncReserve() internal {
+        _BASE_RESERVE_ = _BASE_TOKEN_.balanceOf(address(this));
+        _QUOTE_RESERVE_ = _QUOTE_TOKEN_.balanceOf(address(this));
+    }
 }
diff --git a/contracts/DODOPrivatePool/impl/DPPVault.sol b/contracts/DODOPrivatePool/impl/DPPVault.sol
index 471109f..0783ed4 100644
--- a/contracts/DODOPrivatePool/impl/DPPVault.sol
+++ b/contracts/DODOPrivatePool/impl/DPPVault.sol
@@ -51,12 +51,6 @@ contract DPPVault is DPPStorage {
         _setRState();
     }
 
-    function _syncReserve() internal {
-        _BASE_RESERVE_ = _BASE_TOKEN_.balanceOf(address(this));
-        _QUOTE_RESERVE_ = _QUOTE_TOKEN_.balanceOf(address(this));
-        _setRState();
-    }
-
     function _resetTargetAndReserve() internal {
         _BASE_TARGET_ = _BASE_TOKEN_.balanceOf(address(this));
         _QUOTE_TARGET_ = _QUOTE_TOKEN_.balanceOf(address(this));
diff --git a/contracts/DODOVendingMachine/impl/DVMTrader.sol b/contracts/DODOVendingMachine/impl/DVMTrader.sol
index 4aac393..18bad0d 100644
--- a/contracts/DODOVendingMachine/impl/DVMTrader.sol
+++ b/contracts/DODOVendingMachine/impl/DVMTrader.sol
@@ -48,7 +48,7 @@ contract DVMTrader is DVMVault {
         returns (uint256 receiveQuoteAmount)
     {
         uint256 baseInput = getBaseInput();
-        require(baseInput > 0, 'INSUFFICIENT_BASE_INPUT');
+        require(baseInput > 0, "INSUFFICIENT_BASE_INPUT");
         uint256 mtFee;
         (receiveQuoteAmount, mtFee) = querySellBase(tx.origin, baseInput);
         _transferQuoteOut(to, receiveQuoteAmount);
@@ -65,7 +65,7 @@ contract DVMTrader is DVMVault {
         returns (uint256 receiveBaseAmount)
     {
         uint256 quoteInput = getQuoteInput();
-        require(quoteInput > 0, 'INSUFFICIENT_QUOTE_INPUT');
+        require(quoteInput > 0, "INSUFFICIENT_QUOTE_INPUT");
         uint256 mtFee;
         (receiveBaseAmount, mtFee) = querySellQuote(tx.origin, quoteInput);
         _transferBaseOut(to, receiveBaseAmount);
@@ -88,33 +88,35 @@ contract DVMTrader is DVMVault {
         if (data.length > 0)
             IDODOCallee(assetTo).DVMFlashLoanCall(msg.sender, baseAmount, quoteAmount, data);
 
-        (uint256 baseReserve, uint256 quoteReserve) = getVaultReserve();
         (uint256 baseBalance, uint256 quoteBalance) = getVaultBalance();
 
-        uint256 mtFeeRate = _MT_FEE_RATE_MODEL_.getFeeRate(tx.origin);
-        uint256 lpFeeRate = _LP_FEE_RATE_MODEL_.getFeeRate(tx.origin);
-        if (baseBalance < baseReserve) {
-            uint256 validBaseOut = DecimalMath.divCeil(
-                baseReserve - baseBalance,
-                DecimalMath.ONE.sub(mtFeeRate).sub(lpFeeRate)
-            );
-            baseBalance = baseReserve.sub(validBaseOut);
-            _transferBaseOut(_MAINTAINER_, DecimalMath.mulFloor(validBaseOut, mtFeeRate));
-        }
-        if (quoteBalance < quoteReserve) {
-            uint256 validQuoteOut = DecimalMath.divCeil(
-                quoteReserve - quoteBalance,
-                DecimalMath.ONE.sub(mtFeeRate).sub(lpFeeRate)
-            );
-            quoteBalance = quoteReserve.sub(validQuoteOut);
-            _transferQuoteOut(_MAINTAINER_, DecimalMath.mulFloor(validQuoteOut, mtFeeRate));
-        }
-
+        // no input -> pure loss
         require(
-            calculateBase0(baseBalance, quoteBalance) >= calculateBase0(baseReserve, quoteReserve),
+            baseBalance >= _BASE_RESERVE_ || quoteBalance >= _QUOTE_RESERVE_,
             "FLASH_LOAN_FAILED"
         );
 
+        // no output -> pure profit
+        if (baseBalance >= _BASE_RESERVE_ && quoteBalance >= _QUOTE_RESERVE_) return;
+
+        if (baseBalance < _BASE_RESERVE_) {
+            (uint256 receiveBaseAmount, uint256 mtFee) = querySellQuote(
+                tx.origin,
+                quoteBalance.sub(_QUOTE_RESERVE_)
+            );
+            require(_BASE_RESERVE_.sub(baseBalance) <= receiveBaseAmount, "FLASH_LOAN_FAILED");
+            _transferBaseOut(_MAINTAINER_, mtFee);
+        }
+
+        if (quoteBalance < _QUOTE_RESERVE_) {
+            (uint256 receiveQuoteAmount, uint256 mtFee) = querySellBase(
+                tx.origin,
+                baseBalance.sub(_BASE_RESERVE_)
+            );
+            require(_QUOTE_RESERVE_.sub(quoteBalance) <= receiveQuoteAmount, "FLASH_LOAN_FAILED");
+            _transferQuoteOut(_MAINTAINER_, mtFee);
+        }
+
         _sync();
     }
 
diff --git a/test/DPP/trader.test.ts b/test/DPP/trader.test.ts
index b52a470..3e181b3 100644
--- a/test/DPP/trader.test.ts
+++ b/test/DPP/trader.test.ts
@@ -178,7 +178,35 @@ describe("DPP Trader", () => {
 
 
     it("flash loan", async () => {
+      // buy
+      await ctx.transferQuoteToDPP(trader, decimalStr("200"))
 
+      // buy failed
+      await truffleAssert.reverts(ctx.DPP.methods.flashLoan("1946763594380080788", "0", trader, "0x").send(ctx.sendParam(trader)), "FLASH_LOAN_FAILED")
+
+      // buy succeed
+      await ctx.DPP.methods.flashLoan("1946763594380080787", "0", trader, "0x").send(ctx.sendParam(trader))
+
+      // trader balances
+      assert.equal(
+        await ctx.BASE.methods.balanceOf(trader).call(),
+        "11946763594380080787"
+      );
+
+      // sell
+      await ctx.transferBaseToDPP(trader, decimalStr("1"))
+
+      // sell failed
+      await truffleAssert.reverts(ctx.DPP.methods.flashLoan("0", "103421810640399874604", trader, "0x").send(ctx.sendParam(trader)), "FLASH_LOAN_FAILED")
+
+      // sell succeed
+      await ctx.DPP.methods.flashLoan("0", "103421810640399874603", trader, "0x").send(ctx.sendParam(trader))
+
+      // trader balances
+      assert.equal(
+        await ctx.QUOTE.methods.balanceOf(trader).call(),
+        "903421810640399874603"
+      );
     })
 
     it("revert cases", async () => {
diff --git a/test/DVM/trader.test.ts b/test/DVM/trader.test.ts
index 5381bc1..81de2ce 100644
--- a/test/DVM/trader.test.ts
+++ b/test/DVM/trader.test.ts
@@ -168,6 +168,35 @@ describe("Trader", () => {
     });
 
     it("flash loan", async () => {
+      // buy
+      await ctx.transferQuoteToDVM(trader, decimalStr("200"))
+
+      // buy failed
+      await truffleAssert.reverts(ctx.DVM.methods.flashLoan("1946763594380080788", "0", trader, "0x").send(ctx.sendParam(trader)), "FLASH_LOAN_FAILED")
+
+      // buy succeed
+      await ctx.DVM.methods.flashLoan("1946763594380080787", "0", trader, "0x").send(ctx.sendParam(trader))
+
+      // trader balances
+      assert.equal(
+        await ctx.BASE.methods.balanceOf(trader).call(),
+        "11946763594380080787"
+      );
+
+      // sell
+      await ctx.transferBaseToDVM(trader, decimalStr("1"))
+
+      // sell failed
+      await truffleAssert.reverts(ctx.DVM.methods.flashLoan("0", "103421810640399874604", trader, "0x").send(ctx.sendParam(trader)), "FLASH_LOAN_FAILED")
+
+      // sell succeed
+      await ctx.DVM.methods.flashLoan("0", "103421810640399874603", trader, "0x").send(ctx.sendParam(trader))
+
+      // trader balances
+      assert.equal(
+        await ctx.QUOTE.methods.balanceOf(trader).call(),
+        "903421810640399874603"
+      );
 
     })
 
diff --git a/test/IDODOCallee/DODOCallee.test.ts b/test/IDODOCallee/DODOCallee.test.ts
deleted file mode 100644
index e69de29..0000000