Based on the samples of state-owned listed companies from 2013 to 2020, this paper examines the impact of mixed ownership reform on the maintenance and appreciation of state-owned assets and the regulatory role of national audit. The study reveals that the mixed ownership reform of state-owned enterprises has a significant positive correlation with the maintenance and appreciation of state-owned assets, and the national audit has a positive regulatory effect. Further research shows that there is no significant difference between the state-owned enterprises in the eastern and non-eastern regions in the promotion of the degree of mixed ownership reform on the maintenance and appreciation of state-owned assets and the regulatory role of national audit, which shows that the mixed ownership reform has made phased progress as a whole. Compared with monopoly state-owned enterprises, the mixed ownership reform of competitive state-owned enterprises is much more effective. The research conclusion has certain enlightening significance for the effective promotion of the mixed ownership reform of state-owned enterprises.