Abstract: Based on radiosonde data, ground observation data and European Center reanalysis data, the characteristics and causes of the regional cold wave in Yunnan from February 19 to 22, 2022 were diagnosed and analyzed. The results showed that the daily maximum temperature decreased significantly in the early period of the cold wave, which was a cooling cold wave, and sustained low temperature and snowfall in the later period was a low temperature cold wave. The northwest air flow after the trough guided the cold air to return to the west along the surface high pressure, and pushed the surface cold front to Yunnan with the shear line, which was the main influence system causing the cold wave weather. The cold advection transport at low level was strengthened, and the temperature drop was further increased due to the high temperature in the early stage, which was conducive to the occurrence of cold wave. The convergence area in the lower layer of the atmosphere was deep, the divergence intensity in the middle layer was enhanced, the vertical upward movement developed, and with the water vapor transport of the southwest jet in front of the south trough, there was precipitation in the province. In the area where the ground temperature is close to 0 ℃, the phase of rain and snow was complex, but the zero point line is grounded, the relative humidity of the lower layer is small, and the ice crystal loses the melting mechanism, which is the main reason for the snow weather.