Abstract: By applying the general observations and NCEP reanalysis data,the formation cause of a local sudden rainstorm weather process which occurred in Kunming has been analyzed.Meanwhile,by using the Weather Research and Forecasting(WRF) model,we have done the sensitivity experiments of parameterization scheme.The results show that the feature of unstable atmospheric stratification of up-dry/cold and down-warm/wet,causes the large scale circulation of the rainstorm.Before the rainstorm occurs,the vapor has been transported to the rainstorm area continuously,and by the dynamic mechanism of convergence in lower level and divergence in upper level,the vapor and unstable energy will be accumulated continuously.Finally the rainstorm will be triggered.The satellite cloud image reveals that a MβCS causes the rainstorm directly,and the maximum hourly rainfall occurs in the moving of MβCS.The numerical simulation reveals that the optimal microphysics scheme is Kessler,the optimal parameters scheme is Kain-Fritsch,and the combination of the two schemes can reproduce this kind of rainstorm process effectively.