Abstract: A WC-17Co coating was fabricated on the face of titanium alloy by using high velocity oxy-fuel (HVOF) technology. The bonding properties between WC-17Co coating and Ti-6Al-4V substrate were discussed. The reasons of boundary fracture were analyzed through the microscopic morphology, oxidation behavior, and the form of crack propagation. Critical strain energy release rate Gss of WC-17Co/Ti-6Al-4V is measured by four-point bending test. The low interface bonding strength of WC-17Co/Ti-6Al-4V was ascribed to the increased micro-hardness (322.4 HV) of Ti-6Al-4V after oxidization, so it does not generate apparent deformation when molten particles impact on its surface.