AbstractLow-density urban sprawl is reducing the quality of urbanization, especially in China. Improving the population aggregation degree is an essential means to solve the problem, and in this process, the central urban area plays a vital role. It is necessary to explain the population’s spatiotemporal distribution mechanism and analyze the potential of population aggregation. The study took the central area of Tianjin, China, as an example, and the working framework focused on the comprehensive perspective of the urban built environment, which was divided into four dimensions (spatial construction intensity, spatial function characteristic, spatial accessibility, and spatial ecological quality). A geographically and temporally weighted regression (GTWR) model was first applied to determine the spatiotemporal relationship between the urban built environment and population-density distribution, and then, an urban-population aggregation-potential evaluation model was constructed through bivariate local spatial autocorrelation to analyze the potential for population aggregation. The results showed that spatial construction intensity and function characteristic indicators had the most significant impact intensity and were the main influencing factors, with spatial accessibility and spatial ecological quality indicators as subsidiary factors. Each index had the heterogeneity of influence in both time and space simultaneously, which was manifested in the spatiotemporal nonstationarity of the correlation coefficient. Most of the high-population aggregation-potential areas in the study were single-type high-potential areas, accounting for 37.78%, and were dominated by building density. Based on the mechanism and potential results of population spatiotemporal aggregation, the study provided new planning advice for Chinese cities to achieve better space utilization and sustainable urban development.