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By using the conventional observation data, intensive automatic station data, and the data of NCEP (1°×1°， 4 times per day) and Doppler radar, a local heavy rain occurred in the central Yunnan on 20 June 2017 is analyzed. The results show that the 700 hPa shear line and the ground convergence line were the main weather systems that produced the local torrential rain. The local torrential rain occurred in the weak convection environment where there were lowlevel converges and the middle and upperlevel diverges, and the strong local water vapor convergence in the lower level provided water vapor conditions for the heavy rain. The local torrential rain occurred in the area with the maximum TBB gradient at the edge of the convective cloud cluster. The surface dewpoint temperature increased significantly 6 hours before the storm happens and CAPE also increased significantly. During the heavy rainfall process, there were two rainfall peaks: the first lasted for a long period and mainly caused by the heavy precipitation supercell and mesocyclone; the second lasted for a short period and was weak, mainly caused by multiple convective storms. The Doppler radar charts of the two stages shows the lowcentroid structure, and there was radial velocity formed in the upwind zone, which was about 1 hour ahead of the storm. The precipitation intensity decreased with the disappearance of the upwind zone. The local heavy rain occurred in a terrain, and the heavy rainfall occurred in a valley surrounded by mountains on three sides. The stable and less movement of the convective storm in a bellshaped valley was an important reason for the local torrential rain.