Abstract: Cu/Al composite strip（Cu accounts for ＞90%） were used, the effects of different annealing process on the microstructure and properties of Cu/Al composite plate were studied by orthogonal experiment. The change of interface layer and the diffusion of interface elements were observed and analyzed by scanning electron microscope（SEM） and energy dispersive spectroscopy（EDS）. The mechanical properties and conductivity of the composite strip were measured by tensile test, conductivity test and peeling test. The results show that the thickness of interface layer increases with the increase of annealing temperature and time, and the optimum annealing process is 380 ℃×10 h, the thickness of the interfacial layer reaches 14.17 μm, and the peeling strength reaches the maximum of 34 N/mm. XRD results show that Cu₉Al₄, Cu₄Al, Cu₃Al₂ and CuAl₂ are the main phases in the interface layer. Diffusion annealing treatment reduces the tensile strength of Cu/Al composites, increases plasticity, and improves the conductivity and peeling strength.