Abstract: The correct description of urban surface features, especially the correct treatment of the surface micro-topography, is a critical factor influencing the accuracy of the urban local flooding model． Surface digital elevation model (DEM) is usually used to describe the surface topography． From the demand for constructing urban local flooding model, this paper proposed an approach to overcome defects of traditional DEM． It includes the processing of surface sink points, urban roads expression and architecture expression． The research lays the foundation for professionals to correctly handle the urban surface micro-topographical features and building urban local flooding model．