Abstract: The diffusion-reaction zones of Al/Cu/Mg diffusion couples made by inlaying method were researched to identify their characteric by means of back-scattered electron images of Scanning electron microscope and Electrion microprobe analysis. The results indicate that sintering temperature plays a prime role in the development of the number of phase layers. Five ternary intermetallic compounds were obtained at 450 ℃,there are Al6CuMg4,Al7Cu3Mg6,Al2CuMg,Al5Cu6Mg2 and Cu5Al3.