Abstract: Construction standard of water and soil conservation project in the mountainous area of South Ningxia is low, the aging of the project is serious, and the utilization efficiency of local water resources is low. In order to solve this problem, a closure and slow-release ecological system has been built locally. The closure and slow-release ecological system is composed of a series of closure and slow-release ecological dams arranged reasonably in space. The closure and slow-release ecological dam is a water and soil conservation measure for improving small silt dams. Its main biological and engineering measures have synergistic effects on watershed hydrology. In order to reveal the impact of closure and slow-release ecological system on the runoff of small watersheds and provide a reference for the new development of the silt dam in the future, CASC2D-SED model of the watershed is constructed by taking camel forest watershed as the research object, the parameters are calibrated and verified based on measured rainfall-runoff data, the changes of underlying surface conditions after the project is completed are determined by field investigation and test, and these conditions are substituted into the model to couple the project with the model. By comparing the measured and simulated comparison and analysis of runoff before and after the project construction, and combining the calculation and analysis of runoff with runoff coefficient of the river basin, the influence of the project on the river basin runoff is determined. After the model is built, the deterministic coefficient of the rate periodicity and verification period are above 0.7, the absolute value of relative error of flood peak is within 20%, and the fitting degree is good. According to the calculation and analysis of runoff and runoff coefficient of the river basin, after the construction of the project, the runoff and runoff coefficient of the river basin have increased significantly, and the runoff coefficient has increased by about 3.5%. The basin model is used to simulate the basin flood process before project construction, and the coupling model is used to simulate the basin flood process after project construction. The results show that the project can effectively reduce the peak flow and reduce the peak flow by about 30%. The closure and slow-release ecological project can significantly increase the runoff coefficient of the watershed and reduce the flood peak. So, the closure and slow release ecological system can increase the water utilization efficiency and tap the potential of water resources. Moreover, due to the convenient construction and low cost of the project, it can be popularized to a certain extent.