Abstract: The shear properties of graphene/copper composites were systematically studied by molecular dynamics method, including shear elastic modulus, shear yield strength, shear failure strength and shear deformation mechanism. It is found that the addition of graphene significantly improves the shear strength of the graphene/copper composites and the shear strength increases with the increasing of the volume fraction of graphene. The graphene layer in the composites has synergistic effect with the copper layer, i.e. the graphene layer prevents the copper dislocation propagation, and the copper layer blocks the buckling of the graphene structure. The shear properties of the graphene/copper composites with spherical defects were also investigated. The results show that the small size defects with different number and location have little effect on the shear properties of the composites. The graphene/copper composites with small defect still have good performance and application value. But with the increasing of the diameter of the defects, the shear strength of the composites decreases distinctly.