In the post Cold-War era, the chief national development objective of the People's Republic of China is become a major economic power while that of Japan is to become a first-rate political power. Because of their respective objectives and geographical proximity, both cooperation and competition have become important elements in their bilateral relations, though the warmth that permeates their economic ties does not exist in their political relations. This article attempts to outline the factors shaping this cooperative-competitive relationship between mainland China and Japan from the perspective of the changes in their national interests and policies. A brief forecast of their bilateral relations is also provided.