The valley plain has the characteristics of both mountainous hills and plains, with special terrain conditions and frequent floods. In order to improve the drainage capacity of the river valley plain, this article takes the Bihu Plain in the Oujiang River Basin as an example, uses MIKE11 one-dimensional hydrodynamic software to establish a mathematical model of the river network, analyzed the flood and drainage in the river valley plain, studied the impact of Traditional Flood control mode and Flood control mode based on sponge cities concept in regional drainage, analyzes the advantages and disadvantages of different flood control strategies in practical cases, and provides solutions for regional flood control, Summarized and clarified the relationship between urban flood control and watershed flood control.