Abstract: In this paper, the aerial and ground automatic station NCEP data has been used to analyze the heavy rain in Sichuan Province from July 7, 2013 to July 11, 2013. Analyze the effect of atmospheric circulation of each layer, water vapor flux and divergence of moisture flux of low-level, vorticity, divergence, vertical motion of each layer, help us understand the development mechanisms of precipitation under the influence of the southwest vortex. Result shows: Moisture on 850 h Pa mainly from the Bay of Bengal, which was transported from the southwest to Sichuan region, in conjunction with low-level convergence and high-level divergence structure and continuous ascending motion, as well as the formation of the convective instability stratification, precipitation easily occurs.While the southwest vortex of the stability, north-south rotation and other abnormal activities is the main cause of persistent heavy rainfall.On the one hand, constant eastern-moving Plateau trough and cold air from northwest on 500 h Pa, and on the other hand, the obstruction of the western subtropical high trenches makes the southwest vortex develop continuously but confined to the surroundings of the source, and has difficulties to move out of Sichuan. Therefore, it brings continuous heavy rainfall in the western Sichuan plateau edge and the western region of Sichuan Basin.