The acceleration of population aging and the continuous development of social endowment system have an important impact on fertility. Based on the provincial panel data from 2005 to 2021, this paper analyzes the effect and mechanism of population aging and endowment insurance on fertility. The results show that: endowment insurance and population aging inhibit the improvement of fertility level to a certain extent, and the inhibition effect of endowment insurance is more significant; In the long run, we should effectively combine childbearing and endowment insurance, improve the basic endowment insurance system, develop large-scale endowment, avoid the occupation of childbearing resources by endowment, and promote the long-term balanced development of population and social security.