A special weather event over Beijing is simulated,and a series of sensitivity experiments are carried out using a nested grid version of PSU/NCAR's mesoscale model(MM5) with a fine mesh grid size of 15km. It is shown that the MM5 model reproduces successfully the development of the weather process and its relevant mesoscale systems,that latent heat release acts a vital role in the development of the windward waves weather case,that responses to topographic forcing is rather sensitive;and that the store and transportation of the low-level potential unstable energy over Beijing are crucial conditions for the formation and intensification of convection.