Abstract: The modified NCAR/PSU mesoscale model version II (referred to as MM2) is used in this paper. First,the dry and moist version models simulate the structure of a cold front in North China during the summer season. The dry model only simulates the large scale features and the weaker frontal circulation. The moist case is capable of simulating some important features of the mesoscale stream fields. It indicated that if the large scale data is well initialized and model has reasonal model physics processes,it also has the ability to simulate the mesocale features for some systems. The sensitivity tests of the cumulus parameterized scheme indicate that both the factor b of increasing humdity and the vertical heating profile are very sensitive to describing the evolution of system and to forecasting the precipitation.Based on above works,the cumulus parameterized scheme is designed,which includes the downdrafts.The preliminary results show that the new scheme improves the precipitation forecast.