This book starts the research on the reform of delayed retirement policy from four topics: the theory of old-age security, the international comparison of delayed retirement, the research on delayed retirement policy and the realization mechanism of delayed retirement age. Delaying retirement policy reform has become an important strategic choice for the country to comprehensively deepen reform, and will have a significant and far-reaching impact on all areas of society. Therefore, the delayed retirement policy is not only the focus of social concern, but also a research hotspot in academia.