Abstract: The regulatory system of annual report inquiry letters is increasingly recognized as an important means for securities exchanges to regulate the market. To explore the impact of internal control quality on annual report inquiry letters in enterprises, this article is based on the perspective of enterprise response letters, using Stata15 software and a fixed effects model for testing and heterogeneity analysis. Research has found that high-quality internal controls in enterprises can improve response efficiency. Meanwhile, due to differences in the nature of property rights and inquiry questions, the efficiency of their responses also varies. Empirical evidence shows that non-state-owned enterprises have a more positive attitude towards responding to inquiries, and the more serious the nature of the inquiry, the higher the efficiency of responding to internal control quality in enterprises. The research conclusion of this article has positive significance for promoting enterprises to strengthen internal control, improve the quality of accounting information disclosure, and promote the better effectiveness of inquiry supervision system