The rapid urbanization and high density of urban populations has resulted in increasing hydrological and environmental problems. A distribution model was established for an urban area located in Xixian New Area in Shaanxi Province, China to evaluate the hydrological and environmental effects of low-impact development (LID). The results for all simulated rainfall events show that: (1) LID mode could effectively control urban rainstorm runoff and reduce the peak flow, total amounts of runoff and pollution load. Compared with traditional development (TD), the runoff reduction rates were increased by 18.3-34.7%, and total amounts of suspended solids (SS), chemical oxygen demand (COD), total phosphorus (TP), and total nitrogen (TN) were reduced by 42.4~80.3%. (2) The peak concentration was reduced and the appearance time was delayed under LID mode. Compared with TD mode, the reduction rates of all pollutant loads had been remarkably reduced. However, the reduction effects on rainfall runoff and its pollution loads gradually decreased with the design rainfall recurrence periods increased. (3) The linear models between pollution load reduction amount and runoff reduction amount were established, which can be used to predict urban non-point source pollution load for a rainfall event or a given year.