Based on the principal-agent framework， this paper mainly studies the influence of agency conflicts and internal and external governance mechanism on goodwill formation and scale in M&A activities. Taking A-share listed companies from 2012 to 2017 as samples， the empirical test shows that the more serious the management agency conflict is， the larger the scale of goodwill formed through merger and acquisition will be， indicating that corporate goodwill does contain non-economic bubbles. Further research shows that effective internal incentive mechanism and external governance constraint mechanism can weaken the relationship between management agency conflict and goodwill scale. Companies with large agency conflicts are more likely to have a large impairment of goodwill in the subsequent period and negative reflection of corporate performance. The findings are helpful for further objective understanding of the accounting information content of goodwill， and help enterprises to take effective corporate governance mechanism to restrain the formation of unreasonable part of goodwill， so as to reduce the risk of enterprises.