Abstract: Using surface precipitation data, radar data and ERA (ECMWF Re-Analysis)-Interim reanalysis datasets, the extreme precipitation process in Lushan, Ya'an on August 11, 2020 (abbreviation as "08.11") is analyzed from the conditions of dynamic, thermal and water vapor anomalies. The results show that: The extreme precipitation occurredin the process of the northward uplift of the South Asian high pressure ridge line and the eastward strengthening of the plateau trough, with the extreme characteristics of large cumulative rainfall, strong suddenness and high concentration. Strong positive vorticity advection in front of the trough caused strong upward motion. There was no obvious cold air during extreme precipitation, which was a rainstorm in warm area with high precipitation efficiency. The convergence line of boundary layer triggered strong uplift under the combination of high temperature, high humidity and strong unstable energy. During the heavy precipitation process, the wind speed from low level to high level was small. Under the condition of weak wind, the small and medium-sized system MCC was stable and less dynamic, it provided continuous power and water vapor environment for extreme precipitation. Banded echoes were constantly generated form Lushan to Tianquan, the stability of "upwind area" made Lushan Storm Column maintain and strengthen, the wind speed in the middle and lower troposphere was orthogonal to the mountains, which enhances the increasing effect of terrain on precipitation.