The rotating anode target of X-Ray tube can be constituted with Mo diffusion bonded with graphite. The direct diffusion bonding of Mo and graphite without interlayer was conducted, and the microstructures and mechanical properties of the joints were investigated. Moreover, the effects of interlayer and its form on the interface reaction, the microstructures and the joint properties were inspected. The results indicated that the properties of the joints bonded without interlayer were inferior due to the hard and brittle carbide layer formation. The joint microstructures and properties could be improved with interlayer, especially when Ni was used as interlayer. The shear strength of the joint bonded with interlayer could be over the strength of the base material graphite. The different form of the interlayer, had effects on the microstructures and properties of the joints.