This paper analyzes the emerging East Asian regionalism and compares the foreign policies of U.S., China, and Japan, differentiating the two main sides of foreign policy: security policy and foreign economic policy. In Section 1, it principally examines the East Asian regionalism in terms of low politics: the evolution of ASEAN+3, foreign economic policies of these three countries and the establishing process of East Asia Summit. In Section 2, the paper analyzes the East Asian regionalism in terms of high politics: security policies of U.S., China and Japan, the evolution of U.S.-Japan alliance, and the cooperative security in East Asia. Finally, this paper argues that Japan' s foreign policy is characterized by decoupling foreign economic policy from security policy, while U.S. and China carry out the both sides of foreign policy in a body.