In order to better improve the heavy rain forecast accuracy in Chengdu area (30.1°-N31.5 °N, 103°E-104.9°E, samehere in after), based on T639 high resolution (0.28°×0.28°) data and the data of encrypted automatic stations of Chengdu, 15 cases of heavy rainfall indexes for moist helicity in flood season from July to September in 2011 and 2012 were analyzed by statistical method, included the moist helicity indexes of 3 hours, 24 hours strong precipitation occurrence, development and falling area distribution. Two cases of strong precipitation process in Chengdu Region were checked out and scored by using these criteria and threw into the business forecasting work in the flood season. The results showed that distribution of 700 hPa or 850 hPa moist helicity can give good indication to the distribution of rainfall. Heavy rainfall appeared in the positive and negative moist helicity value isoline concentration areas on 700 hPa and close to the positive side, but in the positive area on 850 hPa. When regional heavy rainfall occurs, moist helicity values reached the number of index values(20×10^-11~80×10^-11 Pa·s^-3) for 5~8 times or more in 3 hours interval forecasting field; When the moist helicity values reached the number of index values(20×10^-11~140×10^-11 Pa·s^-3) for 5~8 times or more in 3 hours interval forecasting field, regional torrential rainfall occurs; When moist helicity values for 300×10^-11~500×10^-11 Pa·s ^-3 appeared in different levels, local strong convective weather, such as wind, short-time strong rainfall would possible happen.