Abstract: Using Himawari-8(H8) satellite data, NCEP FNL reanalysis data, surface and upper air observation data, the characteristics of the convective initiation and the triggering mechanism of the rainstorm event occurred in Kunming on July 20,2019 were divided and analyzed. The results are as follows: (1) The 500 Hpa low-vortex shear was the main impact system of the process, and the rapid development of convective cloud and the merger of cloud made precopitation aggravation and continue. (2) In the initial stage of precipition, the convective cloud was low. With the development of the convective clouds, the cooling rate of infrared brightness temperature reached −30 ℃·(30 min)⁻¹, the precipition rapidly enhanced. When the convective cloud top was close to the water vapor top, the temperature difference between water vapor and infrared bright temperature was less than 2 ℃, the precopitation enhanced. The rapid decrease of infrared brightness temperature and the temperature difference between water vapor and infrared brightness was used as a reference indicator for the forecast of short-term heavy precipitation. (3) CAPE shape was elongated, and a certain convection inhibition was easily triggered. When the cold air invaded, the convection developed into deep convection under the cooperation of terrain unlift. The entire layer of moisture reached up to 3554 g·kg⁻¹ and the water vapor inflowed from the north-south sides, which provided advantageous water vapor conditions for this rainstorm.