The Cu/Al diffusion couples were prepared by solid-liquid bonding method. Interfacial microstructure and phase composition were investigated by scanning electron microscope (SEM), energy dispersive spectrometry (EDS) and X-ray differential (XRD). Moreover, the microstructural evolution of Cu/Al interface was quantitatively analyzed on the basis of diffusion theory and phase diagram. The results reveal that: the interface consists ofⅠ(AlCu+Al2Cu), hypereutectic microstructureⅡ[Al2Cu+(α-Al+Al2Cu)] and hypoeutectic microstructure Ⅲ [α-Al+(α-Al+Al2Cu)] from Cu side to Al side accordingly. Further, there are various morphologies of Al2Cu phase formed with the decreasing of Cu concentration. Additionally, the thickness of three diffusion zones is basically identical with the theoretical prediction.