Abstract: NW trending ductile shearing in the Taishan area took place at the end of the Archean, when the tectonic system transformed from ductile plastic deformation to brittle deformation.It belonged to medium high temperature shearing deformation.The characteristics of microstructure and petrochemical composition isocon diagrams of deformed rocks in the shear zone show that the physical changes of the rocks ran through the deformation process while the petrochemical changes only took place in the stage of mylonization . The ductile shearing played an important role in crustal thickening and was a symbolic tectonic event in the cratonization.