Abstract: The impact of Doppler weather radar (DWR) data on the simulation of a heavy rainfall event is examined. The quality control algorithm of DWR developed by Center for Analysis and Prediction of Storms is applied and the threshold for the raw S-band DWR radial velocity is decided. Several commonly seen non-meteorological returns can be removed effectively. The DWR reflectivity data are processed and the regional three-dimensional mosaic is generated using the CINRAD 3D Digital Mosaic System developed by State Key Laboratory of Severe Weather. Retrieval results match well with the observation. The Gridpoint Statistical Interpolation System (GSI) and the Weather Research and forecasting Model version 3.5.1 (WRF) are used to assimilate 46 S-band DWR data to simulate the severe heavy rain cases that occurred in Jun 2013. Numerical experiment results show that about 90% of the radial velocity data after quality control can be assimilated and generate reasonable analysis increments. Results also show that the assimilation of DWR data has a positive impact on the simulation of heavy rainfall. Assimilating radial velocity can enhance the information of mesoscale weather system in initial field and the simulated field, making the simulated wind fields and rainfall location more similar to the observation. Radar reflectivity data are used primarily in a cloud analysis that retrieves the amount of hydrometeors and adjusts in-cloud temperature and moisture. Assimilating radial velocity affects the zonal and vertical winds by adjusting the amount of hydrometers and moisture which have directly influence on generating precipitation. It changes the simulated rainfall intensity. Assimilating radial velocity and reflectivity at the same time can not only reflect the wind filed more reasonably, but also improve the simulation of rainfall intensity and area. In addition, improvements of the precipitation are most notable in the 12-36 h simulation when more effective radar data are available. Both ETS and HSS of experiment assimilating radar data are proved higher than CTRL experiment which only assimilates conventional data.