Abstract: Internal audit helps companies achieve value-added by attestation services, consulting services and improving the risk management etc. We tried to find the main factors influencing the companies value-added of internal auditing in China through the establishment of structural equation model and the solid empirical test which based on on-the-spot interview and samples data from questionnaire survey for 326 companies. The results showed that the quality of internal control, the quality of internal auditing and corporate governance are the main factors influencing the value-added of internal audit; there are interaction relationships between the quality of internal control, the quality of internal audit and the corporate governance.