Based on the MM5 model with four different cloud microphysical schemes(Duhia simple ice,Reisner mix phase,Reisner2 graupel and Schultz microphysical schemes),numerical simulations are carried out to study the cloud physical processes in a rainfall event over Qilian Mountains during 12-13 July 2002.Comparisons among the experiments and against the observations indicate that the simulated rainfall area from the four cloud physical processes are further south than the observed one.Except Reisner2 graupel scheme,other three schemes have little effect on the center of rainfall area,and the intensity of precipitation center is not sensitive to cloud microphysical processes.The explicit precipitation and parameterize precipitation depend on different cloud microphysical processes.Cloud microphysical processes impact on the occurrence time and intensity of strong precipitation by affecting the occurrence/development times and intensity of dynamic conditions.Analysis of the cloud microphysical parameters shows that the processes of the parameters concerned with precipitation are different for the four different schemes.For Duhia simple ice scheme,rain water and cloud water are primary.For Reisner mix phase scheme,the collection of rain water,cloud water,snow and graupel may paly a main role for precipitation,and the coagulation of ice crystal is relatively weak.For Reisner2 graupel scheme,rain water,cloud water,snow,ice and graupel all are concerned with collection and accretion processes.For Schultz microphysical scheme,the collection of ice,snow and graupel is more significant.