Abstract: In the paper, according to the field data the contact relationships of the pre-Sinian strata in the Lesser Qinling Mountains in Shaanxi are analysed. It has been found that distinct angular unconformities exist between the Taihua Group and the Tietonggou Formation and between the Xionger Group and the Gaoshanhe Formation. Both are the products of orogenic movements. The former corresponds to the Songyangian movement, while the latter the Zhongyueian movement. They divide the pre-Sinian System into three major tectonic beds, which differ markedly in formation of original rocks, tectono-magmatic cycle and metamorphic grade.