Abstract：In Feb,1950, China and the former Soviet Union signed Sino soviet Friendly Alliance's mutual Aid Treaty, which symbolized the establishment of alliance relationship between the two countries. From then on, they entered into a friendly and cooperative new period of time. However, after the twentieth party congress held by CPSU, differences between them rose up and intensified progressively, which caused all out confrontation and led to the division of their alliance in fact. The paper thinks, the conflict between former USSR's great power chauvinism and China's seeking for equality was the basical reason for the division; the seperation of internal affairs, which came from their respective exploration of the road to construct socialism was the principal reason; conflicts between their rational interests and strategic thought was the direct reason, and their arguement on ideology was the catalysis which led their alliamce to burst out.
