diff --git a/pkg/backtest/exchange.go b/pkg/backtest/exchange.go
index dfff47791..c5b850d4b 100644
--- a/pkg/backtest/exchange.go
+++ b/pkg/backtest/exchange.go
@@ -167,7 +167,7 @@ func (e *Exchange) QueryOrder(ctx context.Context, q types.OrderQuery) (*types.O
 func (e *Exchange) SubmitOrders(ctx context.Context, orders ...types.SubmitOrder) (createdOrders types.OrderSlice, err error) {
 	for _, order := range orders {
 		symbol := order.Symbol
-		matching, ok := e.MatchingBook(symbol)
+		matching, ok := e.matchingBook(symbol)
 		if !ok {
 			return nil, fmt.Errorf("matching engine is not initialized for symbol %s", symbol)
 		}
@@ -192,7 +192,7 @@ func (e *Exchange) SubmitOrders(ctx context.Context, orders ...types.SubmitOrder
 }
 
 func (e *Exchange) QueryOpenOrders(ctx context.Context, symbol string) (orders []types.Order, err error) {
-	matching, ok := e.MatchingBook(symbol)
+	matching, ok := e.matchingBook(symbol)
 	if !ok {
 		return nil, fmt.Errorf("matching engine is not initialized for symbol %s", symbol)
 	}
@@ -211,7 +211,7 @@ func (e *Exchange) QueryClosedOrders(ctx context.Context, symbol string, since,
 
 func (e *Exchange) CancelOrders(ctx context.Context, orders ...types.Order) error {
 	for _, order := range orders {
-		matching, ok := e.MatchingBook(order.Symbol)
+		matching, ok := e.matchingBook(order.Symbol)
 		if !ok {
 			return fmt.Errorf("matching engine is not initialized for symbol %s", order.Symbol)
 		}
@@ -250,7 +250,7 @@ func (e *Exchange) QueryTrades(ctx context.Context, symbol string, options *type
 }
 
 func (e *Exchange) QueryTicker(ctx context.Context, symbol string) (*types.Ticker, error) {
-	matching, ok := e.MatchingBook(symbol)
+	matching, ok := e.matchingBook(symbol)
 	if !ok {
 		return nil, fmt.Errorf("matching engine is not initialized for symbol %s", symbol)
 	}
@@ -293,7 +293,7 @@ func (e *Exchange) QueryWithdrawHistory(ctx context.Context, asset string, since
 	return nil, nil
 }
 
-func (e *Exchange) MatchingBook(symbol string) (*SimplePriceMatching, bool) {
+func (e *Exchange) matchingBook(symbol string) (*SimplePriceMatching, bool) {
 	e.matchingBooksMutex.Lock()
 	m, ok := e.matchingBooks[symbol]
 	e.matchingBooksMutex.Unlock()
@@ -363,7 +363,7 @@ func (e *Exchange) SubscribeMarketData(startTime, endTime time.Time, extraInterv
 }
 
 func (e *Exchange) ConsumeKLine(k types.KLine, handlers []func(types.KLine, *ExchangeDataSource), src *ExchangeDataSource) {
-	matching, ok := e.MatchingBook(k.Symbol)
+	matching, ok := e.matchingBook(k.Symbol)
 	if !ok {
 		log.Errorf("matching book of %s is not initialized", k.Symbol)
 		return
@@ -381,16 +381,16 @@ func (e *Exchange) ConsumeKLine(k types.KLine, handlers []func(types.KLine, *Exc
 			}
 			// log.Errorf("kline %v, next %v", param.kline, matching.NextKLine)
 			e.MarketDataStream.EmitKLineClosed(param.kline)
-			for _, h := range param.callback {
+			for _, h := range param.callbacks {
 				h(param.kline, param.src)
 			}
 		}
 		matching.ParamCache = make(map[types.Interval]Param)
 	}
 	matching.ParamCache[k.Interval] = Param{
-		callback: handlers,
-		src:      src,
-		kline:    k,
+		callbacks: handlers,
+		src:       src,
+		kline:     k,
 	}
 }
 
diff --git a/pkg/backtest/matching.go b/pkg/backtest/matching.go
index 99279980d..eae117cad 100644
--- a/pkg/backtest/matching.go
+++ b/pkg/backtest/matching.go
@@ -48,9 +48,9 @@ func init() {
 }
 
 type Param struct {
-	callback []func(types.KLine, *ExchangeDataSource)
-	kline    types.KLine
-	src      *ExchangeDataSource
+	callbacks []func(types.KLine, *ExchangeDataSource)
+	kline     types.KLine
+	src       *ExchangeDataSource
 }
 
 // SimplePriceMatching implements a simple kline data driven matching engine for backtest
@@ -193,9 +193,9 @@ func (m *SimplePriceMatching) PlaceOrder(o types.SubmitOrder) (*types.Order, *ty
 			order.Price = m.Market.TruncatePrice(m.LastPrice)
 			price = order.Price
 		} else if order.Type == types.OrderTypeLimit {
-			if m.NextKLine.High.Compare(order.Price) > 0 && order.Side == types.SideTypeBuy {
+			if m.NextKLine != nil && m.NextKLine.High.Compare(order.Price) > 0 && order.Side == types.SideTypeBuy {
 				order.AveragePrice = order.Price
-			} else if m.NextKLine.Low.Compare(order.Price) < 0 && order.Side == types.SideTypeSell {
+			} else if m.NextKLine != nil && m.NextKLine.Low.Compare(order.Price) < 0 && order.Side == types.SideTypeSell {
 				order.AveragePrice = order.Price
 			} else {