Synopsis Mongolia, the only independent state of Central Asia, has a long history of strategic importance. Its geographical location between China and Russia affected its political status in modern times. Its emergence as an independent state in 1921 was due to the Sino-Soviet rivalry for domination there. It was so at the time of the establishment of diplomatic relations between the Republic of China and the Union of Soviet Socialist Republics in 1924 and it was so at the time of the conclusion of the alliance between the Union of Soviet Socialist Republics (USSR) and the People's Republic of China (PRC) in 1950. But it was not so on the occasion of the Sino-Soviet summit in Beijing on 15-18 May 1989. Mongolia between China and the USSR is an attempt to understand the abovementioned development, especially its implications in the context of Mongolia's strategic position between China and the USSR since 1949. This study has been done on the basis of the author's own observations in Mongolia, not only on the traditional resources. The author hopes that his study will contribute, however modestly, to a proper understanding of the importance of Mongolia's position between China and the Soviet Union since 1949.