Since the implementation of family planning policy in China in the 1980s, the sex ratio has increased significantly compared to the previous period in which birth was not controlled. According to data from previous censuses, the sex ratio of births in China were at the third, fourth, fifth, and sixth census data of 107.63, 111.27, 119.92, and 121.2, respectively. From the initial growth rate to the current imbalance of the sex ratio, the family planning policy has directly affected the change of the sex ratio. Since 2002, China has gradually liberalized its fertility policy. However, China ’s sex ratio is still high all over the world. The influence of boys ’preferences and family planning policies has led to a rising sex ratio in China. The imbalance of the sex ratio will cause a series of social problems. For example, the imbalance of the sex ratio will cause men to have a competitive disadvantage in the marriage market and lead to a high savings rate in China.(S. Wei and X. Zhang, 2011).This article first analyzes the current status of China's family planning policies and the current status of pension fund expenditures. Then, we collected and sorted the inter-provincial panel data of 31 provinces in China from 2006 to 2015, and empirically studied the impact of changes in the sex ratio of the population on social pension insurance spending. The population sex ratio was used as the main explanatory variable, and social pension insurance expenditure was used as the explained variable. Based on the consideration of individual effects and time effects, a fixed effect regression was performed on the data. The study found that the population sex ratio showed a significant negative correlation with the level of pension insurance expenditure. That is, by increasing the sex ratio of a unit, the pension insurance expenditure will be reduced by 0.015%, and it is significant at the level of 5%, indicating that the imbalance of the sex ratio will aggravate the country's social security efforts. The per capita disposable income of residents, the proportion of tertiary industry's added value to GDP, the size of the family population has a positive impact on pension insurance expenditure, and the level of education and urbanization of residents has a negative impact on it.The key issue this article attempts to solve is the degree of influence of the population sex ratio on social pension insurance expenditure. The pension insurance expenditure spending is not as low as possible. Keeping it within a certain range will be more conducive to the sustainable development of society. Therefore, it is necessary to transform and upgrade the family planning policy and adjust the policy in a timely manner. At the same time, other policies need to be implemented in cooperation to better improve the social security system.