M & A is one of the current development strategies commonly used by domestic and foreign companies, and it is an important means to enhance corporate competitiveness and increase economic benefits. From the perspective of irrational behavior, this paper collects data on major asset mergers and acquisitions in the A-share market from 2010 to 2018 as a research sample and conducts an empirical analysis. It is found that there is a companion effect in the merger and acquisition decisions of listed companies. The frequency of peer mergers and acquisitions in emerging industries such as information transmission, software and information technology services has a smaller impact on the probability of corporate mergers and acquisitions than in traditional industries such as manufacturing; the peer effect of mergers and acquisitions of companies with a high degree of executive connection is greater than that of a company with a low degree of connection. The companion effect of M & A enterprises is higher than that of low-linked enterprises. It is suggested to strengthen the supervision of irrational behavior of private enterprises, traditional industries, senior management and high-connected enterprises in mergers and acquisitions, so as to avoid the loss of corporate performance caused by blind follow-up.