Taking the data of A share state owned listed companies in Shanghai and Shenzhen from 2012 to 2020 as a sample, this paper takes the audit supervision events implemented by the national audit office as a quasi natural experiment, and empirically tests the impact and mechanism of government audit on the reliability of performance commitment in SOEs’ M & A and major asset reorganization through multi time point double difference model. The results show that: (1) The implementation of government audit can significantly improve the reliability of performance commitment of M&A of state owned enterprises. This conclusion has been effectively verified in all M&A samples and samples excluding performance standards within 5%. And it is still established after a variety of robustness and endogenous tests. (2) Further mechanism test shows that government audit can promote the reliability of performance commitment of M&A of state owned enterprises through its “supervision” effect, and “incremental” effect. However, it does not have a good “spillover” effect on the same industry enterprises that have not been audited. (3) In terms of the economic consequences after the agreed period of performance commitment, government audit significantly improves the long term performance of enterprises with performance commitment, and reduces the risk of goodwill impairment. However, the impact on enterprises with performance commitment is not obvious.