<p>Based on the statistics of the fifth and sixth censuses in China, this paper, which focuses on the spatial distribution characteristics of aging population in China's mega cities, examines the distribution of aging in Beijing, Shanghai, Guangzhou, and Wuhan. In this paper, an Aging Degree Index and an Aging Population Mean Center have been used to analyze the spatial distribution characteristics and spatial variation trends of aging population in mega cities. According to the research, the spatial distribution of aging population shows a faster development tendency of suburbanization from two different perspectives: one tendency is centrifugal spread associated with seniors who are moving from the city center to outer suburb areas, and the other is center concentration where the seniors who lived in the outer suburb areas are moving towards the city center.</p