diff --git a/hikyuu_cpp/hikyuu/trade_sys/moneymanager/MoneyManagerBase.cpp b/hikyuu_cpp/hikyuu/trade_sys/moneymanager/MoneyManagerBase.cpp
index fb7c312f..5e54106b 100644
--- a/hikyuu_cpp/hikyuu/trade_sys/moneymanager/MoneyManagerBase.cpp
+++ b/hikyuu_cpp/hikyuu/trade_sys/moneymanager/MoneyManagerBase.cpp
@@ -139,13 +139,14 @@ double MoneyManagerBase::getBuyNumber(const Datetime& datetime, const Stock& sto
             m_tm->checkin(datetime, roundUp(money - cash, precision));
         }
     } else {
+        int precision = m_tm->getParam<int>("precision");
         CostRecord cost = m_tm->getBuyCost(datetime, stock, price, n);
-        price_t need_cash = n * price + cost.total;
+        price_t need_cash = roundUp(n * price + cost.total, precision);
         price_t current_cash = m_tm->cash(datetime, m_query.kType());
         while (n > min_trade && need_cash > current_cash) {
             n = n - min_trade;
             cost = m_tm->getBuyCost(datetime, stock, price, n);
-            need_cash = n * price + cost.total;
+            need_cash = roundUp(n * price + cost.total, precision);
         }
         n = need_cash > current_cash ? 0 : n;
     }