The study selected listed central enterprise groups from 2007-2017 to empirically examine the effect of internal control on tax avoidance of SOEs and the moderating effect of state audit supervision on the relationship between the two. The study shows that internal control has a governance function that inhibits tax avoidance by SOEs, and that state audit supervision significantly enhances the inhibitory effect of internal control on tax avoidance by SOEs, suggesting that internal control and state audit are important factors in understanding the level of tax burden of SOEs and its changes. Further research found that the governance effect of internal control on tax avoidance was more significant in the group of SOEs with low intensity of regional tax collection and control, low quality of social audit and aggressive tax avoidance; and by decomposing the five elements of internal control, it was found that the inhibitory effect of internal control on tax avoidance was concentrated on the two elements of control activities and information and communication. The analysis of mechanisms suggests that internal controls can serve the governance purpose of discouraging corporate tax avoidance by alleviating the degree of corporate financing constraints.