Abstract: Using automatic station observation data, Doppler radar data, ERA-5 0.25°×0.25° reanalysis data and WRF numerical simulation data, we analyzed the mesoscale environmental conditions, the mesoscale convective systems triggering and maintenance mechanisms of one warm-sector heavy rainfall process in the Wuling Mountains of Chongqing on May 19-20, 2018. The results were as follows: (1) There was no obvious cold air forcing in this process, the baroclinicity is weak, but the boundary layer had high temperature and humidity, and the atmosphere stratification was extremely unstable. (2) The evolution of the mid- and small-scale convective systems of the heavy precipitation in Shiqiao mainly had three stages: the convections scattered into east-west zonal flow, the rainfall near Shiqiao remained quasi-stationary after the break of the zonal flow, and the northeast-southwest zonal flow reconstructed rapidly. (3) The convergence line which distributed along the Wuling Mountains, triggered the thunderstorm. The strong echo of convective cell moved and strengthened along the convergence line, contributing to the formation of the "train effect". (4) The strong thunderstorm cold pool on the eastern mountain top of Shiqiao flowed down the mountain, working together with the warm and humid air currents and topography to maintain the strong precipitation in Shiqiao. (5) Topography played an important role in this heavy precipitation process. The easterly wind near the ground interacted with the mountains in the west of Shiqiao to form a small local cyclonic vortex, which made significant contribution to triggering precipitation. Moreover, due to the blocking effect of the mountains in the east of Shiqiao, the speed of the topographic vortex slowed down, which was conducive to the maintenance of precipitation.