Using the ground meteorological observation data, ERA5 reanalysis data, FY2E satellite and Doppler radar data, a diagnosis and analysis of a severe convective rainstorm occurred in Chaohu on 17 July 2011 is made. The weather analysis shows that the 500hPa deep trough, the 850hPa shear line, and the ground lowpressure were the synoptic scale impact systems of the heavy rain process. The precipitation process occurred in the deep wet and warm clouds, low LCL (Lifting Condensation Level), medium convection instability and weak vertical wind shear. The FY2E satellite cloud image analysis shows that the heavy precipitation process was mainly caused by the merger of multiple mesoscale convective systems in Lake Chaohu, and the shortterm heavy precipitation area mainly fell near the TBB isoline dense area of the mesoscale convective system. The stronger the TBB center intensity, the larger the TBB contour gradient, the stronger the corresponding 1hour precipitation would be. Doppler radar analysis reveals that shortterm heavy precipitation occurred during the merge of two convection echoes. The convective storm moved slowly, and the strong echoes greater than 45 dBz were below 6 km, showing lowlevel strong cyclonic convergence and highlevel divergence. The ground mesoscale convergence line was the trigger of the storm. The diagnostic results of wet potential vorticity show that convective instability below 600 hPa and symmetrical instability above 600 hPa are beneficial to the occurrence and development of heavy rain and mesoscale systems.