Abstract: Cu and Al alloy were bonded by compressiong-diffusion composite connection technology. The welding technics procedure was: Cu and Al alloy be compressed firstly, then diffused on 515℃ for 60 min, and diffuseed 90 min again before hot-pressed. The microstructure was researched by various test methods, such as SEM, EDS, micro-hardness test, XRD and so on. The experiment results indicated that brittle compound CuAl₂ appeared in the interface and a new component was created between Cu & welding, which looks like a bright belt. Electric performance of joint was between Cu and Al alloy, that could be satisfied with practical application.