The paper, through a historical review of the multilateral relations among Northeast Asian countries, indicates the fact that the region has been being one of the high-light areas in the political frame of the world as well as the major place where the superpowers' competition has been taken place since the early of this century. Now the tendency of economic regionalization is getting more and more evident with the changes of economic and political situation in the world,the bilateral as well as multilateral relations among Northeast Asian states are being improved, the political circumstance for mutual confidence and cooperation is coming appear, and the cooperated development of Tumen river is becoming a focus arousing the attentions from most parts of the world* The involvement of UNDP into the Tumen river project has greatly pushed the process of regional cooperation and joint development among countries in the area. The realization of such a project will undoubtedly bring the Northeast Asian nations a great deal of economic benefits and promote the economic growth as well as the political stability in the area.