Be/HR-1 and Be/Cu/HR-1 stainless steel were bonded respectively by vacuum hot pressing. The hot deformation microstructures and mechanical properties of their joints in the diffusion zone were analyzed by means of optical microscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD) and material testing machines. The relationship between deformation microstructures as well as pressure and properties were discussed. Results show that hot pressing can lead to diffusion creep and grain boundary slip of the materials, and influence the grain size and amounts of intermetallic compounds in the diffusion bonding zones. Hot pressing should not be conducted under the critical pressure or critical strain which will cause maximum grain size in the matrix. The intermetallic compounds along grain boundary can be reduced by reducing holding pressure or time, and the bonding strength can be improved. The melting points of the phases formed through reactive diffusion of Be/Cu/HR-l are much lower than that of the matrix, and the deformation can be controlled by reducing holding pressure or temperature.