Abstract: Based on the global reanalysis data of NECP FNL and the precipitation data of regional automatic stations in Sichuan Province, eight typical rainstorm weather processes in Beichuan Qiang Autonomous County from 2016 to 2019 were selected to diagnose and analyze the circulation background, water vapor condition, dynamic condition and thermal condition of the rainstorm process. The results show that: (1) Beichuan is mainly characterized by topographic rainstorm, multi-night rain and short-term heavy rainfall. (2) The circulation pattern of rainstorm is mainly ' high in the east and low in the west ' and ' two high shears '. Vortex, short wave trough and subtropical high interact with each other. Near the ground, the thermal low pressure in eastern Sichuan and southern Chongqing intersects with the cold air invaded by the northwest path through the Tibetan Plateau. (3) The 850 hPa low-level jet of the global rainstorm is mostly southward, and the axis center is located at 106°E. If the warm advection is dominant, the rainfall level is large. 850hPa low level jet of the regional rainstorm is not obvious, 700hPa jet position is north, the intensity is weak, cold and warm advection is similar. (4) Beichuan is often located in the convergence center of water vapor flux, especially when the heavy rain and extra-heavy rain occur, the upward vertical velocity and vertical helicity increase significantly in Beichuan. At the same time, the low altitude area of 105°~110°E is a high temperature and high humidity area, while the high altitude area is dry and cold potential and unstable., the rain area is located at the edge of the energy front area.