Abstract: On the basis of the digital elevation model and digital line graphic(1:50 000)and digital orthophoto map(2.5 m resolution) data sources and so on, approximately 0.53 million small catchments are divided covering 8.68 million km² of territorial area, the hierarchical coding system and topological relationship are built for the river basins, the main characteristic parameters are analyzed, and the national small catchment parameter database is constructed including the basic characteristics, meteorology, rainstorm, runoff generation and confluence characteristics of small catchments.The results have provided basic data and technical supports for the national flash flood disaster prevention and control.