Abstract: In this paper,research on diffusion bonding of MB15 magnesium alloy was carried out according to atomic diffusion theory.Three kinds of method of removal oxide film of MB15 were used,and the best one was chose.Gleeble-1500 testing machine is used in the diffusion bonding experiment on the superplastic MB15.In addition,shear experiments of welded joints are carried out with electronic universal testing machine,and the optimum diffusion bonding parameters are obtained.The microstructures of the welded joints are analyzed through metallographic microscopy and SEM.It's deduced that the micro-mechanism of diffusion bonding is the slide of original grain boundaries caused by atom diffusion and the growth of grains of the MB15 superplastic material,sound joint was obtained through sufficient diffusion of the surface atom of the joints.