Abstract: Based on the application of the low-frequency synoptic map(LFSM),this paper analyzed the active characteristics of low-frequency weather systems on 500hPa for the summer strong precipitation process in Sichuan basin,by the data of summer precipitation data between 2008 and 2013,wind data on 500hPa. The low-frequency wind series during strong precipitation process were calculated by Empirical Orthogonal Function(EOF). The main spatial pattern and the wind allocation of the main low-frequency weather systems were studied. Eight low-frequency key regions,very related with precipitation process in forecast area,were divided by the spatial position,distribution and frequency of low-frequency weather systems.They are the active region of Northwest Pacific high and typhoon at low latitude,South China Sea,Arabian Sea and Bay of Bengal,the area from Mongolia to the middle of Yellow River,Tibetan Plateau,The periods of each key region is calculated. It shows that the periods in low latitude key regions(1,2,3) and Tibetan Plateau key region(6) are short,while long in high latitude key regions(4,5,7,8). We analyzed the allocation and history period of low-frequency weather systems in each key region during strong precipitation process,gained the relationship between precipitation process and the activity of low-frequency weather systems,established the forecast model by the method of low-Frequency synoptic map for predicting the strong precipitation process. With this method,we forecasted the strong precipitation process in Sichuan Basin in the summer of 2013. We found that we forecasted good during June and middle of July,but not good from late July to August,when it's hot and dry.