Based on the data of encrypted automatic weather stations, radiosonde data, Doppler weather radar data and ERA5 reanalysis data, this paper analyzes the precipitation characteristics, circulation situation, physical field and mesoscale convective system evolution of a local heavy precipitation process on the night of May 20, 2023 in Zunyi, Guizhou Province. The dynamic and thermodynamic effects of the medium and small scale landforms in Loushan Mountain during this process are discussed. The results show that: (1) the process occurred under the influence of 200hPa divergence and convergence of low trough and low vortex shear in the middle and lower layers. The continuous upward movement and high temperature and high humidity in the whole layer are the important reasons for the long precipitation time and large cumulative rainfall in the process. (2) The topography of Dalou Mountain makes the 850hPa southeast warm and humid air gather on the windward side, resulting in the θse and relative humidity gradient large value area along the Dalou mountain range in the northeast-southwest distribution, there is a θse and relative humidity large value area on the east side of the mountain range, that is, the unstable state of high energy and high humidity atmospheric junction is always maintained in the heavy rain area, providing favorable conditions for the occurrence of heavy precipitation. (3) The geostrophic deviation of the friction layer makes the 850hPa southerly air flow turn to southeast air flow when it passes over the central mountainous area of Guizhou. When the southeast air flow crosses Dalou Mountain, it forms a lee trough due to the conservation of potential vortex, and finally forms a stable north-south shear in southeast Sichuan. The shear is often triggered by convection near the shear, and under the action of the guiding air, the convection moves eastward and affects the northern area of Zunyi City downstream. (4) The steady flow of low-level southeast air from the north of Dalou mountain range between Xishui and Tongzi "V" shaped terrain across the south side of the mountain, due to the north end of the west branch of Loushan Mountain and the topography of Jinfou Mountain, formed a maximum value center of water vapor flux, and formed a water vapor convergence zone downwind, resulting in water vapor accumulation effect. Convection is triggered at the overlapping position between the northern part of the surface convergence line and the large value area of the divergence gradient of water vapor flux.