Top management turnover in the post-acquisition phase has significant effect on corporate acquisition performance.However,findings of these studies are inconsistent.Most studies have been done from the perspective of enterprise resources theory,organizational learning theory,corporate culture theory and transaction cost theory to explore the relationship between post-acquisition TMT and firm performance.However,this area of research is rarely investigated from the institutional theory. The institutional theory emphasizes that each organization is embedded in its institutional environment in which it is subject to various institutional factors.Especially in China and other emerging markets,these institutional factors may have direct or indirect effect on corporate strategic behavior and performance.In addition,corporate different strategic choices and behaviors will result in different degrees of legitimacy of these institutional factors. The current study argues that the social recognition obtained from all the stakeholders represent the legitimacy of the corporate behavior or the firm itself.Different groups of stakeholders judge the legitimacy of a firm based different perspectives and interests.Different strategic actions may result in different levels of legitimacy,which will further stimulate or constrain corporate strategic behavior and thus affect the firm performance.This paper argues that previous study ignored the influence of institutional factors.This article attempts to reveal the relationships among post-acquisition TMT,and the legitimacy and firm performance from the institutional theory perspective From the perspective of institutional theory,this paper introduced the concept of legitimacy and investigate the relationships among post-acquisition TMT,legitimacy and acquisition performance based on a sample of 123 acquisitions.The results showed that post-acquisition TMT had significant negative influence on both external and internal legitimacy,which had significant positive effect on acquisition performance.This paper explained the effect of post-acquisition TMT on acquisition caused by the legitimacy.Therefore,it is important to assess the potential impact in order to avoid weakening the corporate legitimacy and performance when replacing the original manager after an acquisition.In order to achieve the desired objective of acquisitions,enterprises need to develop suitable acquisition strategies to obtain high level of both external and internal legitimacies.In addition,the findings further support the key role of top managers in the implementation of corporate strategy.This study further confirmed that the institutional factors,particularly the legitimacy of corporate behavior,have significant influence on afirm's strategic behavior and performance. This study not only enriches the research field in the relationship between post-acquisition TMT and acquisition performance,but also uses the institutional theory to explain the strategic behavior of Chinese firms and corporate performance.The results can have theoretical contribution to the areas,including corporate decisions on top management replacement and enhancing acquisition performance after acquisitions.