As the world's most populous country of old people, China became one of the countries with an aging population society in 2000. Demographic transitions influenced by population aging have caused many economic and social problems and been attracting increasing attention throughout China, and are emerging as an important issue in most developing countries. However, as the issue of population aging only began to unfold at the beginning of the 21st century for developing countries, the existing studies on the relationship between demographic transition and economic growth mainly focus on developed countries. Therefore, there are only a few studies on the impact of demographic transition on economic growth in developing countries. The population aging and the phenomenon of labor shortage since the beginning of the 21st century indicate that the demographic dividend due to the low labor cost may have diminished in the near future, which may have a negative impact on China's sustainable growth. Demographic transition is a long-term tendency, whose influence on China's economy may be felt some time later, impacting its macroeconomic environment. This paper tries to quantify the economic effects in the context of demographic transition using the recursive dynamic computable general equilibrium (CGE) model.  The shock of demographic changes in the simulation includes such basic scenarios as population aging, gender shifts, urbanization and human capital structure that contribute to real economic development. A comparative scenario with demographic change simulation other than population aging is adopted for capturing the real impact of population aging. In order to quantify the economic and social effect of government demographic-related policies, another five scenarios are designed to test the impact of different policy measures on the economic growth.  The results from the CGE model reveal that population aging does gradually slow down China's economic growth to 5.513% from 2025 to 2030. All the demographic-related policies may help to offset the negative effect of population aging. Among those policies, the rise of the education level, the improvement of the human capital accumulation, and the increase of the number of high-tech workers will turn out to be the most effective measures for keeping the sustainable growth of China. The extension of the retirement age is only an expedient measure, and urbanization without full citizenization is the least effective. Therefore, it is suggested that the government take such measures as effective population policies, increased spending on education for human capital accumulation and higher labor productivity, and the cultivation of innovative talents to stimulate the second demographic dividend. In addition, relevant measures to address urbanization, such as ensuring migrant's citizenship, improving the educational system, and enhancing social security and medical security may be helpful for offsetting the negative effect by population aging.