Using rotated empirical orthogonal f unction (REOF) method, the summer standardized precipitation field in Southwest China is divided objectively into 5 regions. Based on this, the long-term trend of each region summer precipitation anomaly is analyzed. It is found that the summer precipitation fields in 5 regions have distinct characteristics of interdecadal change in the recent 50 years. The long-term trend of Chuandong, Chuanxi and Guizhou's precipitation is not distinct,but that of Sichuan basin's and Yunnan's is markedly drying.