Abstract: The drainage system of rainwater pipes serves as the primary channel for urban drainage, and its capacity is significantly influenced by pipeline silting and street inlet clogging. Understanding the extent of street inlet clogging and pipeline silting on the network's drainage capacity is crucial for evaluating the development process of urban flooding. Based on the GAST-SWMM coupled model, the drainage process and surface water volume in the study area of Longwangmiao, Lubei District, Tangshan City, were simulated and analyzed under diverse conditions of street inlet clogging and pipeline silting. The results indicate that as pipeline silting and street inlet clogging worsen, the drainage capacity of the network gradually decreases, and this trend becomes increasingly evident. When there is no pipeline silting, as street inlet clogging increases from 0 to 75%,the peak flow decreases by an average of 5.30% to 37.8% compared to no blockage, while surface water volume rises by an average of 2.48% to 14.6%.Similarly,when there is no clogging at the street inlet, as pipeline silting increases from 0 to 75%,the peak flow decreases by an average of 20.9% to 84.6%,and surface water volume rises by an average of 4.46% to 24.1%.Furthermore,when one factor intensifies to a significant level, the influence of the other factor on the drainage capacity of the network will relatively weaken. These findings provide a foundation for analyzing the drainage capacity of rainwater pipes under various conditions and for preventing water-related disasters.