Recent rapid urbanization has broad impact on the contemporary urban environment. Preserving the natural environment has become the central issues in the world. The main concern of this paper is to address the importance of social function of green space. Some results of a survey conducted among visitors of urban parks in Mianyang city in Sichuan Province are presented and discussed. The results confirm that open space experiences have a positives influence on psychological and mental health. Urban green space verifies beliefs about stress-reduction benefits and mental health, and advances social intercommunication. Finally, the monetary evaluation methods of urban green space, such as contingent valuation method, hedonic pricing method, travel cost method, are discussed.