From the integration of audit, this paper studies whether the corporate tax aggressiveness is reduced or not, with financial statement and internal control being audited by different accounting firms. Furthermore, with the standardization of internal control system and external financial statements auditing in China, this paper probes into the role they play in the reduction of taxes aggressiveness respectively, and the interaction effect of the two. Taking A-share listed companies in Shanghai and Shenzhen securities exchange from 2011 to 2015 as research objects, using multiple linear regression method, this paper finds that: integration-free audit can actually make tax aggressiveness rise; high quality of internal control or external financial statements auditing can independently inhibit enterprise tax radical behavior. A further study shows that internal control and external financial statements auditing play an alternative role in inhibiting enterprise tax aggressiveness. Our research conclusion expands the influence of internal and external governance mechanisms on tax aggressiveness, and has important practical significance for effective use of internal and external resources to manage corporate tax avoidance.