Abstract: The effect of surface roughness of Ti-6Al-4V alloy on the bonding strength of tungsten carbide (WC-17Co) coatings sprayed by high velocity oxygen fuel (HVOF) was studied. Different sand blasting processes were used to generate different surface roughness with 22.003, 20.845 and 14.765 μm for No.1, No.2 and No.3 specimens, respectively. The WC-17Co coating with a thickness of 0.3 mm was deposited on the surface of titanium alloy by HVOF technology. The three-point bending test was performed on the WC-17Co/Ti-6Al-4V sample, and the interface morphology was observed by a scanning electron microscope. It was found that cracks propagated seriously at the interface of No. 3 specimen, resulting in the coating peeling off. No. 2 sample showed the best bonding properties. The four-point bending method was used to test the fracture energy release rates between the coating and the substrate, and the values of release rate were 239.7, 259.0 and 200.1 J/m2for three specimens, respectively.