By means of the new generation numerical forecast model WRF(Weather Research Forecast) and MM5 used widely,a simulation study is conducted on a heavy rainfall process occurred on 3 to 4 August 2002 in Liaoning Province.The results indicate that WRF can rather successfully reflect the circumfluence background in the upper or lower level which induced the rainfall and the rainfall distribution.The comparative analysis of the simulation results made by means of WRF and MM5 shows that owing to the superiority of the WRF's dynamic framwork,WRF has better ability to simulate the mesoscale weather system in this heavy rainfall process than MM5 does under the condition of the same physical processes and same pre-processing;the area and intensity of the simulated precipitation by WRF is closer to the fact.