In Population Journal, No.5, 2021, Li Guangqin, Feng Yafang and Gong Yanlei suggest that city size has a significant positive impact on the age of first marriage, and the age of first marriage increases by 0.635 years when the city size increases by 1%. According to the estimation of subsample in age structure and gender, it is found that city size has a positive effect on the first marriage age of the post-60s, post-70s and post-80s samples, and the coefficient shows an increasing trend, but the effect on the pre-60s samples is not significant, which indicates that with the change of the times, the influence degree of city size on the age of first marriage gradually deepens, slightly for men but significantly for women. City size has a positive impact on the age of first marriage through the house price mechanism, and the effect of the house price mechanism on men is greater than that on women. The educational mechanism is reflected in the fact that the first marriage age of those with a high educational background is later, and the educational mechanism has a greater effect on women than men.