With the rapid urbanization and development in transitional urban China, the mega-region as a spatial type of resource integration and its successive spatial organizational patterns have played an increasingly important role in city-region development. This paper mainly reviews and summarizes the research on urban spatial organization from urban geography, urban and regional planning. In this research, using data from the year of 1990, 1995, 2000, 2005, and 2010 for the Pearl River Delta (PRD) mega-region, we attempt to establish a comprehensive index system to calculate the processes of spatial organization and structural patterns over the last 20 years by the method of Global Principal Component Analysis (GPCA). The results of the study show that the factors of urban economic, physical, and population have contributed significantly to evolutions of spatial organization. Furthermore, the PRD mega- regional spatial organization experienced monocentric (single-center), duocentric (double-center), and polycentric (multiple-center) development patterns throughout its development evolution. Finally, according to qualitative and quantitative analysis, this paper endeavors to explain the dynamic mechanism of spatial organization transitional processes and spatial structure patterns from the perspectives of five dimensions:globalization, regionalization, commercialization, urbanization, and decentralization.