All potential subset regression models were used to forecast experiment of the beginning of the rainy season in Yunnan province.The grid point data of 500 hPa and SST during the periods from Jan.to Dec.next before this year and from Jan.to Mar.this year were selected for the influent factors.The factors combined with rainfall at weather stations in Yunnan province were used to built the optimum subset regression model.The model was applied to forecast the rainfall of rainy season in 1998 and 1999.The model forecast accurate is better than the stepwise regression.