Abstract: Numerical simulations of two heavy rainfall cases in the Changjiang Huaihe river basin have been camrried with radar data incorporating into the PSU/NCAR mesoscale model. The radar data are used to change initial humidity analysis obtained by conventional radiosound data and then simulations are performed and compared with the control cases. Results show that both of the heavy rainfall distribution and its maximum amounts in sensitivity cases are further improved than those without using radar data. It implies that the enhancement of humidity by radar data and subsequent divergence circulation and ascending motion at the middle and lower troposphere over the rainfall region is essential for improving the results of heavy rainfall numerical simulations.