Abstract: In this paper using a nested fine mesh model over complex topograph and the ECMWF's grided point data of 2.5°×2.5°in July of 1981,the,sih sets of numerical experiment schemes of with and without types were designed and their 48-hour numerical simulations of the extremely intense rainstorm and soutawest vortex in Julv of 1981 were run.The results of numerical simulations show that the model has a quite good performace for forecasting of heavy rain and southwest vortex.In the developing of the heavy rainstorm and southwest vortex in July of 1981,the release of latent heat of precipitation plays the most important rule,the effect of barrier of Tibetan Plateau has an important rule,and the fluxes of surface sensible and latent heat,surface friction and lateral friction in boundary layer have a certain contributions to the development of southwest vortex,intensifing of upward motion,and the heavy rainfall as well.