By taking one minute high frequent trading data of Stock Index Futures contract IF1112 of Shanghai and Shenzhen 300, according to certain regulation, trading volume is decomposed into open position trading volume, close position trading volume and change position trading volume to measure market volatility by certain methods, the difference in the impact of different types of decomposed trading volume on market volatility of stock index futures is studied, and the obtained conclusion is that the decomposed trading volume contains more incremental information to explain market volatility than that of undecomposed trading volume, that all of the decomposed trading volumes have positive effects on the volatility, whose influential order from strong to weak is open position trading volume, change position trading volume and close position trading volume. 