Magnesium alloys AZ31B plates and pure titanium TA2 plates were bonded successfully through explosive welding. The microstructure and composition of the interface were examined by means of optical microscope (OM), scanning electron microscopy (SEM) and energy dispersive spectroscope (EDS). To explore the process of element diffusion between AZ31B and TA2, the composite plates were annealed at different temperature. Furthermore, the mechanical behavior of the composite plates was evaluated. The results show that straight and wavy interface coexisted on the bonding area. The degree of the element diffusion became obvious when heating at 450?C and 490?C for 4h and 8h. The hardness of AZ31B and TA2 was increased significantly due to the plastic deformation and the strain hardening. The mechanical properties of the composite plates were found significantly improved compared to that of base plate AZ31B.