Abstract: The heavy rainfall over the Jiang Huai basin in 1991 is divided into three Meiyu stages. Employing grid point data of objective analyses from State Meteorological Center, the relationship between the intensity, advancement/retreat of tropical and subtropical monsoon, and heavy rain during the Meiyu is diagnosed with the method of EOF. The analyses show that the first and the second heavy rainfall is mainly related to the tropical monsoon over the East Asia, the third are mainly associated with Indian monsoon. The confrontation of two tropical monsoon in the tropics between 100°E and 120°E is favourable for them into Chinese continent and generate heavy rainfall there.