Recognizing that the broader structure of East Asia’s regional order is going to change, this paper assumes that there are three major factors to drive and facilitate the East Asian order: (1) An existing security architecture comprised of various bilateral and multilateral mechanisms; (2) the role of America in adjusting the current security multilateralism to lead to it remaining cooperative and/or competitive; and (3) the bilateral relationship of the two powers, the United States and China. The paper argues that East Asian order has been and will be determined by the changing state of Sino-U.S. relations. Then it explores what relationship the United States and China engage in and where it is directed. The next section discusses what effect the Sino-U.S. relationship has on the security order in East Asia focusing on the major multilateral security arrangements as seen in Figure 1. To do this, the two distinct multilateral security mechanisms, the U.S.-Japan-Australia Trilateral Strategic Dialogue (TSD) and the Shanghai Cooperation Organization (SCO), will be analyzed. Additionally, as a bridge between the United States and China for security cooperation, the Korea-China-Japan Tripartite Cooperation Dialogue (TCD) will be explored. The future of both Sino-U.S. relations and its relations with the East Asian security order are dealt with in the conclusion. Since the current state of U.S.-China relations is a more complicated, lovehate relationship in locked interdependency, the East Asian order is characterized as a foggy, complex hybrid system. Until a power transition between the United States and China comes close to the threshold, the order will be led more by U.S. chosen bilateralism than Chinese preferred multilateralism. As the Obama administration came into office signaling greater enthusiasm for a multilateral enterprise, Washington’s concern over multilateral security architecture in the region will increase. The viability of a multilateral security institution in East Asia, supported by and with the participation of the United States, will become critical as a non-confrontational way to tame China’s rising power. As a result the Tripartite Cooperation Dialogue (TCD) among South Korea,China and Japan, and the Six-Party Talks will probably become influential as multilateral institutions in which the United States and China both share common strategic interests in East Asia. This development would lead the TCD to become a pivotal security mechanism. This then would contribute to freeing East Asian order of a hybrid and complex system.