Test for mediating effect is an important method in social science research. In this paper, we applied mediating effect test in corporate acquisition research. Acquisition is one of the most important ways to expand a company, especially in emerging markets. From the perspective of institutional view, we made an empirical research on the relationship between geographic and institutional factors and the acquisition performance based on a sample of acquisitions in China. We found that acquisition legitimacy based on different region, including external and internal legitimacy, has positive effect on acquisition performance. We conclude that cross-region acquisition has negative influence on external legitimacy of acquisition, while having no significant influence on internal legitimacy of acquisition.