To study the metamorphic-deformation condition of rocks in ductile of shear zone is an important step to investigate the orogenic process and mechanism. Based on the study of characteristics of dislocations and the types of dynamic recrystallization of garnets in garnet-mica schists in Tongbai Mountains, east section of Shangdan fault (Shangnan-Danfeng fault) belt, the types of the plastic deformation, the deformation mechanism and the condition of deformation of garnets are identified. The garnets had been subjected to early medium-grade regional metamorphism, and then formed dislocations with high density and subgrains under the strong stress in the formation of shear zone, finally occurred plastic deformation.