In this paper, diffusion bonding of ZK60 superplastic material is investigated according to atom diffusion law. Gleeble-1500 testing machine is used in the diffusion bonding processing on the superplastic ZK60. In additional, shear tests of bonding joints are carried out on electronic universal testing machine. The optimized diffusion bonding conditions are obtained: a bonding time of 90 min at 653K at a pressure of 20MPa. The microstructures of the joints are observed through OM and SEM. It is concluded that the mechanism of diffusion bonding of the ZK60 superplastic material is the slide of original grain boundaries caused by atom diffusion and the grain growth, and sound joints with high shear strength are obtained through sufficient diffusion of the interface atoms.