Abstract:The SWMM model, taking the Beiyang area of the coastal city P in Fujian Province as the research area, was used to simulate the current situation of the drainage capacity of urban water and waterlogging distribution in the region when it suffers from the most unfavorable 24 h rainfall in 30 years. On the basis of the simulated results, the background water system in the region would be adjusted. The urban drainage and waterlogging control system would be optimized by optimizing the drainage direction of the water system, reconstructing the river network for drainage and waterlogging controlling, and transforming the new storage area. The optimized drainage and waterlogging control system could not only adjust the current north-south drainage to east-west drainage so as to weaken the tidal top support; but also improve the water system storage capacity and drainage capacity based on the optimal main river channel scale and the number of newly opened discharges. At last, the amount of water remaining caused by the tidal top support would be collected according to the position of the reclamation area and the storage volume. It could be shown form the results that the optimized drainage and waterlogging control system not only effectively solves the current situation of 41,945,200 m3 of water, but also increases the flood discharge by 2.25 times, which has greatly strengthened the drainage capacity of the water system. On the other hand, the problem of drainage and waterlogging prevention in the Beiyang area of P city has also been effectively solved.