The heavy rainfall during 8～9 June 1998 is simulated by using the non hydrostatic mesoscale MM5(V3). The discriminable scale rainfall is simulated by using the Reisner Graupel scheme. Results show that the Reisner Graupel scheme has a better ability to simulate the microphysical process . During the period of the maximal precipitation, the most important sources for the rainwater are the graupel and cloudwater. And the cloudwater′s accretion is the main microphysical process for the graupel.