Abstract: The precipitation Extreme Forecast Index(EFI) from ECMWF global ensemble prediction system can indicate extreme weather events,and this paper researches the heavy rain prediction in Sichuan Basin during summer(June-September) by using this characteristic. Comprehensively considering heavy rain TS,ETS scores corresponding to different EFI threshold and the occurrence frequency of top score threshold,we get the best EFI threshold of heavy rain prediction,the result shows that the thresholds of aging of 24h,48h,72h,96h,120h which are predicted from 8: 00am(UTC+8) are 0.5\0.6,0.5,0.4\0.5,0.4,0.2\0.3,and the thresholds of aging of 24 h,48h,72 h,96h,120hwhich are predicted from 8: 00pm(UTC+8) are 0.5,0.4\0.5,0.4\0.5,0.3\0.4,0.1\0.3,and the examination shows these thresholds have good indicative significance to heavy rain prediction.