By using the optimum correction method,the forecasting of short-rang area mean rainfall of the six drainage areas in the upper reaches of the Changjiang River is done based on correcting the MAPS precipitation numerical forecasting. The operational experiments from June to October show that accuracy of routine mean area rainfall is higher about 15% than that of MAPS,and accuracy of heavy mean area rainfall is higher about 18% than that of MAPS , and the percentage of hits is about 48%.So,it has good effect.