Social security is an important government function for people’s livelihoods, and with economic and social development governments are increasingly focusing on the improvement of efficiency in the use of funds when making decisions on fiscal decentralization. As there is no consensus on whether fiscal decentralization at the expenditure end promotes or hinders the growth of efficiency. Therefore, this paper adopts a three-stage super-efficient non-radial (SBM-DDF) model to assess the efficiency of fiscal social security expenditures at each provincial level in China from 2014 to 2021 and comparatively analyze its regional variability. On this basis, the impact of fiscal social security expenditure fiscal expenditure decentralization on fiscal social security expenditure efficiency and the spatial spillover effects of the two are analyzed through the Spatial Durbin Model (SDM). The results show that in the second stage, after excluding the interference of environmental factors and random factors, the efficiency of most of the provinces has been improved, and regionally speaking, the mean value of the comprehensive technical level of the eastern, northeastern, central and western regions is 1.279, 0.962, 0.967, 0.971, respectively, with obvious differences; among the spatial influencing factors, fiscal decentralization, the scale of fiscal social security expenditure, and fiscal pressure have a positive effect on the efficiency of fiscal social security expenditures in this region, while fiscal pressure has a positive effect on the efficiency of fiscal social security expenditures. Fiscal social security expenditure efficiency has a positive effect, while among them the spatial spillover effect of the general revenue of local finance and the level of social security on neighboring regions is negative; the degree of influence of fiscal decentralization on the efficiency is ranked from low to high, east<central<western<northeastern. Based on the measurement results, we try to put forward targeted policy recommendations for improving the efficiency of China's fiscal social security expenditure, optimizing the structure of fiscal expenditure decentralization and promoting the coordinated development of the realization of the government's social security function and fiscal decentralization decision-making. It not only helps to improve the utilization efficiency of government resources, but also provides a scientific basis for the fiscal management and policy making of each country in order to achieve better social and economic benefits.
