Abstract: To identify the water environment problems in small mountainous urban watersheds, this paper seeks appropriate solutions. By taking the DS Creek in a mountain city as an example, its water quality and quantity characteristics and corresponding environmental problems are studied. The results show that the comprehensive pollution index qi of the upper, middle and lower reaches of DS Creek is 0.78, 1.9 and 1.65, respectively. And the main pollutant is the discharge of sewage along the creek. Every year, it’s about 560 000 m~3 sewage water and 4.06 million groundwater that finally runs into the wastewater treatment plant, and about 990 000 m~3 mixed rainwater and sewage discharges into the Yangtze River. Based on the above analysis, a comprehensive water environment management engineering system in mountain urban watersheds is constructed with the core concept of “mountain water diversion-sewage diversion-ecological restoration-intelligent flow interception.” It is also expected that this case study can provide a reference for the water environment management of other mountain cities, and improve the water ecological environment as a whole.