This research reviews the current state of the environmental problems in Northeastern Asia and emphasizes the necessity of building a sustainable regime of multilateral environmental cooperation. The Process and problems of multilateral environmental cooperation system are briefly discussed. This research stresses the importance of contractual environment that enhances the level of enforcement of international environmental agreement. Within the contractual environment, international regimes can support the parties of conference to build up administrative capacity and scientific technology to cope with transborder pollution problems. Some policy proposals such as cooperation among central governments and local governments, and the participation of NGOs are suggested.