Abstract: Using NCEP 1°×1°reanalysis data,national automatic station surface data,fy4a cloud top temperature data,the regional rainstorm process under the joint action of westerly trough and typhoon in Sichuan Basin is analyzed. The results show that: (1) the main influence system of this process is westerly trough and typhoon,which formed the deformation field favorable for frontogenesis in Sichuan Basin. (2)The center of the deformation field Leshan produced a regional heavy rain. The eastern part of the basin is located in the frontogenetic area,which causes the rain belt to move eastward. (3)Typhoon contributed a lot of water vapor to this process. The westerly trough and topography forcing promote the rain belt to distribute in Northeast-southwest . (4) The surface convergence line produced by the cold air behind the westerly trough and the easterly air flow around the typhoon is an important factor for triggering MCS in Leshan.