Abstract: Under the backdrop of low impact development and sponge city construction, more and more mountain parks have been endowed with the function of ecological sponge. The water environment optimization is not only helpful when solving its own stormwater problems, but also to conserve water resources, preserve water and soil, and reduce the risk of urban flood. Guided by the concept of Sponge City and based on the hydrological characteristics of mountain parks and the hydrological process analysis, this study puts forward the strategies of zoning and grading regulation from the source to the end for rainwater control and utilization in mountain parks water environment optimization design. Taking Guanyao and Lijia Mountain Parks in Nanjing City as examples, it discusses practical applications of water environment optimization design methods. The hydrological simulation results show that it can better meet the construction standards of sponge cities, delay the confluence rate and time, promote the infiltration and utilization of rainwater, and help to optimize the design of water environment for mountain parks of similar scale in urban built-up areas.