Abstract: The Pajiang River Flood Storage and Detention Area(PRSDA) is the only national flood storage and detention area in the Pearl River Basin. It is important to change its single flood control function to a multifunctional wetland with flood regulation and storage, pollutant degradation, and natural tourism in the new historical period. In this paper, a novel wetland construction model summarized as "three cores and one belt" was proposed. This model used the three existing sub-watersheds and two new barrage gates, which can not only realize the construction of different types of wetlands according to local conditions, but also retain the maximum flood storage capacity. In addition, a two-dimensional water flow mathematical model was used to simulate the impact of wetland construction on the flood storage and detention function. The simulation results showed that this newly wetland construction model had little impact on flood storage, which guaranteed the performance of the flood detention function of PRSDA. The results can provide important references for similar research on flood storage and detention areas.