Abstract: Magmatic activity was strong in the southern part of the Sonid Left Banner, Inner Mongolia. Paleozoic plutons outcrop over large tracts. There are a total of 52 plutons of varying size, covering an area of about 239 km 2. In light of the principle for the hierarchical division, mineral composition and textures and structures, the plutonic rocks may be divided into 12 units, which are incorporated into three super units. On the basis of the geological, petrochemical and REE geochemical characteristics of granitoids in the study area, the author discusses their evolution and formation environment.