Abstract: Rainstorms in the southeastern coastal area of China are mainly caused by two different synoptic systems,and the corresponding floods generated by these two system of storms are termed as rainstorm flood. Based on the literature review, this paper proposes that the rainstorms in different synoptic systems should be classified with typhoon rainstorm and non-typhoon rainstorm,respectively. These two type of rainstorms should be studied separately,because different type of rainstorms occur in different time,and have different characteristics of spatial distributions,as well as area rainfall and rainfall intensities. Accordingly,regional floods are classified as typhoon and non-typhoon rainstorm floods,so as to reveal the characteristics of watershed flood under the mixed influence of the two types of floods.