In 2015, the China State Council in its 13th Five-Year Plan for Economic and Social Development strategically initiated the Guangdong-Hong Kong-Macau Greater Bay Area, with emphasis on strengthening its role in economic development and its powerful synergy with the all-important The Belt and Road Initiative (BRI) in the country and globally. The Greater Bay Area is a unique mega city region situated at the Pearl River Delta, covering the 11 9 mainland cities +2 special administrative regions (Hong Kong and Macau) cities. However, few studies examined the bay area under a unique institutional and economic context. This study aims to examine regional integration and spatial connection that affect the growth and success of the megacity region using network analysis. Particularly, it analyzed the centrality of human movements, traffic flow and railway network through visualization of the results from Tencent (QQ) Location Big Data, railway service and census data. The study reveals that the vital contributor to the formation and success of the Greater Bay Area is its rapid growth of transport infrastructure and capacities, particularly high-speed railway, promoting free flowing of the key factors. Strong spatial and transport connection critically harness regional integration and boosting viable development of the Greater Bay Area. Guangzhou-Shenzhen-Hong Kong has shaped a triangle structure. The findings provide planning recommendation and policy implications for city planners and policy makers for regional governance and cooperation in mainland China, Hong Kong and worldwide. •The Greater Bay Area strengthening economic development, with 9 mainland cities + 2 special administrative regions;•Spatial connection of human movements, traffic flow, and transport network denote the degree of regional integration;•Transport infrastructure promote factors freely flowing and contribute to the formation and success of a megacity region;•Integrated infrastructure network raises the Greater Bay Area to the world-class megacity region;•One-hour rail transit forms the megacity region and enhances the flows between the east and west bay area.