The Springtime Southern Branch Trough (SSBT) is generated by the dynamic forcing of the Qinghai-Xizang Plateau, which own abnormal interdecadal variability, and which may be closely related to the anomaly of precipitation in China. The intensity and east/west position of the SSBT and the pertinence between these are analyzed and the corresponding interdecadal variation of precipitation and atmospheric circulation in China, whose interdecadal variation in last 65 years are discussed as well, using the monthly average of reanalyzed data from NCEP/NCAR, combined with monthly precipitation data of 596 observation stations provided, and by employing the methods such as mutation inspection, composition analysis, etc. The results of the analysis indicate that the intensity and position of SSBT is characterized by interdecadal variability, its intensity have a weak mutation process in the late 1970s, and its position was sudden changed from east to west in the early 1990s. And the mutation before(after) the intensity of SSBT is, the stronger (weaker) the SSBT is, while the mutation before(after) the position is, the easter (wester) the SSBT leans, and the precipitation of the Yellow River basin, the middle and lower parts of the Yangtze River and its northern /southern areas increases (decreases), while it apparently drops (rises) in Qinghai-Xizang Plateau and its surrounding area, by using before and after the period of the intensity and position of SSBT. Besides, the relationship between mutation before /after the period of intensity /position and atmospheric circulation, vertical movement, water vapor is also very significant, which explains the reason for the difference of precipitation in China. Then on the base of these, the concept frame of interdecadal relationship with precipitation and atmospheric circulation in SSBT is summarized. These results are helpful to better provide more scientific basis for how and why the spring climate change and climate prediction of China.