As an important new regional social formations, global city regions have re-scaled localized network connections of cities and created challenges for traditional urban planning, management and governance. The issue about How the global city region’s boundary to be delineated still remains to be addressed. In this paper, three geographical scales of network activity in Melbourne global city region were studied, using the concept of peri-urban area, commuting patterns and international tourist day-trip between Melbourne and its hinterland. The result shows that global city region’s boundary is multi-scale and fluid, and it is determined by different intersecting regional to global scales of dynamic flows of people and connections. And last using this finding of the research, the paper examined the defined boundary of Wuhan city circle, in order to give some guidelines to Wuhan city circle development. This finding of the research could give some guidelines for delineation of global city region’s or cheng shi qun’s boundary and making of planning strategies.