Accounting is an important part of the modern economy and society, and accounting informatization has gradually become the development trend of an accounting system. Government fiscal expenditure efficiency is also significantly affected by accounting automation. The study improves the DEA-BBC model to measure the efficiency of fiscal expenditure and adopts the PSM-DID model to construct the model of the effect of accounting informatization on the efficiency of fiscal expenditure according to the theory of government cost accounting and accounting informatization. The effect of government accounting information technology on fiscal expenditure efficiency is empirically studied. Government cost accounting information is selected as the explanatory variable, fiscal expenditure efficiency is selected as the explanatory variable, and control variables are introduced for regression analysis. The mean value of fiscal expenditure efficiency is 0.743, the minimum value is 0.216, the maximum value is 1.000, and the standard deviation is 0.230. The coefficient of government cost accounting informatization is 0.058 before adding control variables, but it increases to 0.065 after adding control variables. For every 1% decrease in government cost accounting informatization, the proportion of fiscal expenditure, the proportion of education expenditure, medical expenditure share, and social security and employment expenditure share rise by 1.1568, -0.4135, -0.2764, and -0.5011 units, respectively. The higher the government’s financial self-sufficiency and the smaller the government, the more efficient fiscal expenditures.