Abstract: Based on the Weather Research and Forecast model(WRF) and three-dimensional data assimilation system(WRF 3D-var), assimilating radar reflectivity factor directly, on October 8, 2010 occurred in the process of rainstorm in Yunnan province, 3D-var and numerical simulation experiment was carried out. Results show that the assimilation radar data without any data assimilation, relatively stretching south location, relatively close to precipitation. Different horizontal resolution radar reflectivity data assimilation, the horizontal resolution of 0.1 degrees after the reflectivity of data assimilation, simulated rainfall relative to other solutions closer to observation. Vertically to choose those of 3500 m and 6000 m height, greater influence on the location of the precipitation and precipitation intensity. In this case a "vertical" level within the selected in the 1000m, 2000m, 3000m, 3500m, 4000m, 5000m, 7000m, 8000m of radar reflectivity data, model simulated precipitation closer to observation.