Abstract: In view of the increasingly serious ecological and environmental problems, this research takes the promulgation and implementation of the national standard Urban Green Space Planning Standard (GB/T 51346—2019), as well as Shanghai as an example, to systematically explore the evolution stage, performance characteristics and influence mechanism with the “complexity” theory. The results show that the urban green space system in Shanghai has three complex evolution stages: creation and maintenance, spatial expansion and organic evolution; two performance features: composition complexity and structural complexity, and two aspects of influence mechanism: start-up mechanism, action mechanism. It is thus to provide guidance for collaborative integration of complex urban green space system, and promote sustainable and healthy development of the urban green space system.