Based on the model of Basso et al， this paper uses data on fertility rate， age structure and financial development in 31 provinces of China over the period 2005-2016 to test the relationship between fertility rate， age structure and financial development after introducing the mechanism of fertility rate and financial development with the basic and extend model. The results of regression show that 1） the fertility rate and age structure are strong negatively with lower financial development， after controlling for several factors， other dependence variable and independence variable and using other estimators， the conclusion is still valid， and it’s in accord with “the Old-age Security Hypothesis” theory. And 2） the fertility rate and age structure are strongly positive with financial development as the result of human capital scarcity in the special regions which the policy of China’s family planning is more weakened. Therefore， putting financial reform and development in advance， banking sectors should improve the financial service， increase supply of financial products and optimize bank site layout to meet various the needs of financial services arising from the change of demographic conditions.