After the Asian financial crisis, the relationship between China and ASEAN has been strengthened; meanwhile, the influence of U.S. in Southeast Asia has been gradually decreased. The rise of China challenges status quo in the region. According to the Neo-realism, national interests depend on national power to put into effect. China and U.S. compete through cooperation with ASEAN in political, economical, traditional and untraditional security and sub-region fields which shape the new order in Southeast Asia. This thesis is divided into five parts and the conclusion of analysis could be as the policy recommendation for the government of R.O.C.¡¦s decision making on Southeast Asia policy.