As of 2007, by virtue of three decades of continuous economic growth, China has joined the ranks of the United States and Japan to form the top three largest economies in the world. Each of the three states' comprehensive strength also tops the world's list; their obvious strengths ensure that they become major players in Northeast Asia. Indeed,in this age of globalization, the three states have found themselves increasingly drawn into the region, where their respective interests converge. Nonetheless, many problems still plagued Sino-U.S. and Sino-Japanese relations. To create a better understanding of the current political dynamics in Northeast Asia, this paper reviews international relations in Northeast Asia with respect to these three states and their relations through the two major remnants of Cold War in the region: the Korean Peninsula and the Taiwan Strait. Through analyzing the two cases, this article seeks to unpack the roles played by Sino-U.S. and Sino-Japanese relations in the formation and evolution of the two issues, from their origins till today. This analysis is made in the hope of promoting strategic trust amongst the three states, and with it, the peaceful co-prosperity in Northeast Asia.