Globalization in business has become increasingly common, so stronger company that is seeking for growth tends to merge and acquire other companies since it is more beneficial to take over an existing firm's operations and niche compared to expanding on its own. Integration shortly after merger and acquisition is key to a company¡¦s long-term success, because top-management team must alter an organization¡¦s structure and establish new strategies to adjust to the rapid changing environment. Therefore, we can conclude that the role of top-management teams during the process of mergers and acquisitions is critical. After merger and acquisition, whether or not the top-management team of the target firm should be replaced remains a good question. Not only should the working ability and the accomplishment of the top-management teams be considered, but other internal and external reasons that might affect this alteration should also be considered. This research looks to discuss why the top-management team for the target firm should or should not remain in the office. We¡¦ve selected acquisition firm and target firm from the listed companies at the stock exchange market, over-the-counter market, and emerging stock market in 1997 to 2006 to be our study sample. We will try to figure out the retained ratio for the top management teams by using regression model analysis. The result of this study shows that the type of M & A, the experience of the acquisition firm, and the type of industry they are in have great impact on the retained ratio of the top-management teams.