Through the vacuum diffusion welding SiCp/ZL101 aluminum with Cu interlayer, the effect of welding parameter and the thickness of Cu on the welded joint property was investigated, and the optimal welding parameters were put forward at the same time. The microstructure of joint was analyzed by means of optical-microscope, scanning electron microscope in order to study the relationship between the macro-properties of joint and the microstructure. The results show that diffusion welding with Cu interlayer could be used for welding aluminum matrix composites SiCp/ZL101 successfully.