Abstract: A continuous heavy rain process at Jianghuai and Hangjiahu Plains is diagnosed with a new method of curved surface fitting (NMOCSF). Some valuable standpoints are presented. Combining with the weather situation, the formation of the quasi-stationary North China high and its contribution to the continuous heavy rain process over Jianghuai and Hangjiahu plains are discussed. It is pointed out that special attention should be given to the intensity and the position of the quasi-stationary North China high during the Meiyu season around Jianghuai and Hangjiahu plains. Once the block-up feature forms, a continuous heavy rain process will probably takes place in a large area.