Abstract: The characteristics of microstructure and mechanical properties of the Mg/Al alloy joint by diffusion bonding with a Zn interlayer were studied by means of metalloscopy, X-ray diffraction, electron probe microanalysis and mechanical property test.Investigations showed that the Mg/Al alloy joint by diffusion bonding with Zn interlayer consists of a multilayer sandwich structure, including the transition zone of Zn-Al, the residual Zn interlayer, as well as the transition zone of Zn-Mg.The transition zone of Zn-Al is composed mainly of a solid solution structure, while the Zn-Mg transition zone has a relative larger dimension after a rapid eutectic reaction.The addition of zinc interlayer inhibits the inter-diffusion of Mg and Al alloy efficiently.The Zn-Mg transition zone constitutes the main part of the joint and consists of Mg and the new phases formed are Mg₂Zn₁₁ and MgZn₂ intermetallic compound.According to the phase constitution analyses executed on each side of the fracture face, it was deduced that the fracture of Mg/Al alloy joint located around the interface of Zn-Mg transition zone.The average shear strength of Mg/Al alloy joints diffusion bonded with Zn interlayer reaches 70 MPa and exceeds that of the joints bonded without Zn interlayer enormously.