Abstract: Sino-U. S. relations have been complicated and fluctuating over the past century,showing the basic logic of friendship,aggression and normalization.Sino-US relations are influenced by many factors such as international pattern,social system,ideology and historical tradition,in which national strength and national interests play a decisive role.Analyzing from the various appearances of Sino-US relations,we can see that the coexistence of friendship and aggression,the interlacing of the both sides and the third parties,the coexistence of cooperation and conflict,and the confrontation between radicalization and the bottom line are regular manifestations.Sino-US relations are extremely complex and uncertain.Judging,evaluating and predicting Sino-US relations should have a historical perspective,dialectical thinking and strategic height,and should not be simplistic or absolute.

Key words: Sino-U. S. relations, state interest, social system