To address the challenge of obtaining high-resolution topographic data for urban flood simulation, a method for constructing high-precision terrain was proposed by integrating multi-source data, including drainage network data, road data, and building data. Taking the area surrounding the Longwangmiao River in Tangshan City as a case study validation area, an urban stormwater model (GAST-SWMM coupled model) was developed based on the digital elevation model (DEM) constructed by the proposed method, and was used to simulate the stormwater processes under two different rainfall events. The simulated waterlogging positions closely match the actual ones. For one of the rainfall events, the Nash-Sutcliffe efficiencies for the water levels at two manholes reach 0.92 and 0.87, respectively, with relative peak water level errors of 3.35% and 3.63%. These verify the effectiveness of the proposed method, indicating that the DEM constructed using this method can accurately reflect the topographic features of the study area and meet the accuracy requirements for urban flood simulations.