Since so called the late 1997 IMF economic crisis in Korea, the M&A has been used as a method of restructuring the corporate governance in Korean companies and the means of maximizing the stockholders's interests that could make the management to improve the corporate governance. However, because of the increasing ratio of the foreign capital, comparing it to the ratio of domestic capital in the Korean capital market resulted from the Korean government's policy that made possible the foreign capital's free investment to the domestic market after the economic crisis, most domestic companies in Korea have felt that the foreign capital have continuously threatened themselves with the anytime-possibility of the hostile takeover. Right now in Korea even the hostile takeover has been launched, the target company can't use any defense method against the hostile takeover because the related Korean laws do not have anything about it. That is the reason why, recently, the need of changing the M&A system in Korea, exactly the need of introduction of defense measures, has been continuously increased. According to this recent trend the Korean government decided to introduce some defense measures such as the poison pill and the dual class stock in near future. However, the introduction of the dual class stock has been criticized because the dual class stock allows the unfair voting right to the very same class stocks against the principle of "1 stock 1 voting right" under the Korean Commercial Code. So, if when it is introduced it needs to be cured with some different method such as the "tenure voting" system. In this aspect, the Article will review the U.S. case related to the tenure voting system in order to take into account it just in case for the introduction of the dual class stock with hoping the improvement of the M&A market system in Korea.