Abstract: The shielding effect of urban buildings under the action of wind field directly affects the process of precipitation runoff.To improve the accuracy of urban stormwater simulation, it is necessary to uncover the unique runoff characteristics of built-up areas under the action of wind field and establish corresponding calculation methods.The runoff surface of built-up areas was divided into horizontal and vertical runoff surfaces, and the rainfall inclination angle caused by the wind field was calculated based on computational fluid dynamics theory.Geometric relationships were integrated to determine the distribution of inclined rainfall on the horizontal and vertical runoff surfaces.Based on the runoff theory, the runoff of the two types of runoff surfaces was calculated and formed the runoff calculation method of built-up areas.The method was coupled into the storm water management model (SWMM) and verified in the experimental watershed.The results showed that: ① the modified SWMM had higher Nash model efficiency coefficient than the original SWMM, and simulated flood peak better; ② the values of some key parameters, such as soil saturated conductivity, obtained via the modified model were more appropriate; ③ the modified model was more stable for runoff simulation of built-up areas under different meteorological conditions.Therefore, this method can improve the simulation accuracy of runoff in built-up areas.