This paper uses the A-share data of listed companies listed on the Shanghai and Shenzhen stock exchanges from 2012 to 2016 and uses the Xtlogit model to test the relationship between managers’ overconfidence and M&A (mergers and acquisitions) decisions, and also to test the relationship between directors’ vigilance and managers’ overconfidence and M&A decisions, and the corresponding robustness test was carried out using the Xtprobit model. The study found that managers’ overconfidence can significantly promote M&A, and board vigilance can significantly moderate the relationship between managers’ overconfidence and M&A decision-making, and can inhibit M&A caused by managers’ overconfidence.