The paper takes listed central enterprise groups from 2007 to 2017 as research subjects to empirically test the impact of national audit and internal control on the value preservation and appreciation of state owned enterprises assets and the synergistic effect of national audit and internal control. The research shows that national audit and internal control conduce to promote the value preservation and appreciation of state owned enterprises assets; national audit and internal control have a substitutive effect in promoting the value preservation and appreciation of state owned enterprises assets. Further research finds that national audit has lag effect and regional heterogeneity on the value preservation and appreciation of state owned enterprises assets. Through the influence mechanism research, we find that the substitution effect is mixed with the intermediary effect, and the substitution relationship between internal control and national audit is not only reflected in the overall policy net effect of national audit, but also reflected in each subdivision level of national audit.