In order to study the improvements of the numerical weather forecast model with radar data assimilation on precipitation forecast, in this paper, an experiment is performed to simulate the Meiyu Front precipitation event during the period of June 26—28, 2015 in the Jianghuai area.The precipitation features and synoptic situation of the event are described with emphasis on the evolution of mesoscale convective systems which contribute greatly to the rainfall.The WRF mode is applied to perform this simulation.After the control experiment, the 3DVAR radar data assimilation scheme is executed.After 15 h spin-up, the sensitivity experiments for len_scaling and var_scaling of background error covariance matrix are performed respectively.The optimal len_scaling is 0.5, and optimal var_scaling is 0.7.By setting the optimal len, var and assimilation time-step of 30 min and 1 h, experiments of assimilating reflectivity factor, radial velocity individually and simultaneously are implemented.The results from the analyses on the water vapor, dynamic and precipitation fields reveal the following:1) assimilating radar data can effectively improve precipitation forecast, 2) assimilating both radar reflectivity factor and radial velocity yields superior precipitation forecast, and 3) higher frequency of assimilating radar data yields superior precipitation forecast.