Abstract: This paper presents a structured DEM generalization by catchment area combination.Thevalley catchment areas are used as the link between the abstract conception of valley and concreteDEM grid points.The minor valley branches are deleted by the Tpfer law and the valley catchmentareas are combined based on the deleted valley network.Then the resulting DEM is interpolated basedon the catchment boundary line(containing three types of basic terrain skeleton information:ridge,mountain and saddle)and the valley line.Experiments show that a DEM reconstructed by this methodcan delete minor terrain characteristics while preserving main characteristics.