Abstract: Due to the complex terrain in Sichuan, it is easy to trigger convection, and the frequency of heavy rain is high. It is very important to study the macro and micro physical characteristics of heavy rain in Sichuan. The GPM data is used to study the structural characteristics of the heavy rainstorm in Sichuan region on 21 May 2018. The results show that the heavy rainstorm was caused by an meso-α-scale convective system. The sample ratio of stratiform cloud precipitation to convective cloud precipitation was 2.5:1, convective cloud precipitation rate was 5 times that of stratiform cloud precipitation. The strong vertical shear of the ambient wind field led to the difference between the location of the maximum rain water content and the location of the maximum cloud ice content. The value of high frequency of reflectivity factor for convective cloud precipitation varied significantly with height than that of stratiform cloud precipitation. The particle number concentration parameter and the effective particle radius reflected that the process of coalescence growth of droplets was remarkable in convective cloud in the range of 4~7 km, and the process of evaporation and fragmentation of raindrop below 4 km was significant. The ranges of particle number concentration parameters and particle effective radius in stratiform clouds were narrower than those of convective clouds, and the changes with height were not obvious.