Based on APARCH and ST-GARCH model,a new kind of asymmetric GARCH family model was introduced which is called ST-APAPRCH.In contrast with APARCH model,more GARCH family models are included,and news is processed more smoothly.In contrast with ST-GARCH model,the power characteristics of yield volatility in different markets were taken into account.Empirical researches were conducted with the return of LLDPE futures,and the results show that ST-APARCH model can better demonstrate the volatility characteristics of LLDPE futures market compared with GARCH,GJR-GARCH or APARCH model,especially the complex leverage effect caused by the shock of news.