Abstract: Based on the data of hourly rainfall, sounding, radar and ground observation of short-time heavy rainfall cases that occurred in Kunming during 1981—2015, the temporal distribution, critical influencing systems, physical quantity and radar observation characteristics of short-time heavy rainfall in rainy season were analyzed. The results indicated that the short-time heavy rainfall in Kunming has a distinct hourly change. A special period from 19:00 to 05:00 the next morning witnesses the continual short-time heavy rainfall, with its peak at 02:00. The convergence line on the ground and the shear line on 700 hPa are the key influencing systems of short-time heavy rainfall in Kunming. When 500 hPa was accompanied by the low pressure trough or high pressure convergence zone, the synoptic situation would easily lead to the short-time heavy rainfall in Kunming. These physical conditions are most conducive to the short-time heavy rainfall: on 700 hPa, the specific humidity greater than 10.0 g·kg⁻¹, the dew-point spread less than 3 degrees centigrade, the pseudo-equivalent temperature equal to 75 degrees centigrade and the SI index less than 0.1. On the other hand, the following radar observation features are the early warning index of short-time heavy rainfall: they are the cumulus and massive radar echo with 40—45 dBz maximum value, the lower center and top height less than 8 km, the corresponding radial velocity with meso-scale convergence or low altitude jet characteristics.