To measure the relationship between building patterns and waterlogging inundation characteristics in Zhengzhou City, using the urban architectural pattern index to characterize the urban architectural pattern, an evaluation index system for urban building patterns was developed considering basic morphological features, spatial distribution features, correlation features, and distance-related features. The urban waterlogging model was established to simulate waterlogging processes in the old urban area of Jinshui District, Zhengzhou City under different return periods and waterlogging characteristics under different building pattern levels were analyzed. The indicators that significantly affect waterlogging characteristics under different rainfall return periods were identified, and the impact of three-dimensional building features on waterlogging was further explored. The results indicate that the building pattern in the old urban area of Jinshui District, Zhengzhou City presents a spatial pattern of high in the north and low in the south. Enhancing the building pattern level contributes positively to inundation mitigation, whereas such effectiveness has a threshold limit. Rainfall with a 3a return period serves as the critical breakpoint triggering abrupt pressure rise of urban drainage systems. Under low-return-period rainfall