Abstract: Using the concept of the second method of Liapunov stability theory, a Liapunov function δ2 S related to the differential equations of atmospheric disturbance is obtained. Form the symbol of the product of Liapunov functionδ2 S multiplied by its differential , the stability of the system can be determined and the occurrence area and intensity of heavy rain are diagnosed. Using this method the experimental forecast for heavy rain is made from June to August of 1993 in the area of three Gores of China. The results show that the forecast accuracy is 5/8.