The regional divergence in population development is an outcome of aging, which also interacts with regional disparities to result in the phenomenon of "growing old before getting rich" in some regions. Such a characteristic combined by aging and regional disparities represents both a specific case within the general trend of aging and a structural attribute commonly present in aging. Differences in demographic transitions and the population migration between countries or regions, if sufficiently large, will inevitably lead to differentials in demographic properties and regional divergence in population development. Using international experiences as a reference background, this paper analyzes the current status, characteristics, and causes of regional divergence of population in China and explains double effects, namely convergence and divergence, caused by population reallocation among regions. Under the implementation of regional balanced development strategies and the trend of regional divergence of population, the factors contributing to inter-provincial development gaps have become increasingly diversified, with population-related factors gradually emerging as key constraints. To address the developmental challenges associated with regional divergence of population, this paper proposes policy suggestions including: promoting the equalization of basic public services across regions regardless of the status quo of the economy and population, leveraging reforms of the household registration system to foster social mobility, and placing human-centered comprehensive development at the core to create the necessary conditions for the lagging-behinds to seize opportunities to catch up.