In this paper, the V2O5 film was coated on the diamond surface by adopting sol-gel method to improve the wettability of the vitrified bond to diamond and the mechanical properties of the vitrified diamond composites. The results show that a uniform and compact V2O5 film formed on the diamond surface at a temperature of 600 degrees C by heat treatment when V2O5 sol had a viscosity of 2 mPa center dot s. During the process of heat treatment, the unsaturated carbon atoms on the diamond surface combined with V2O5 film to form O-V-C and V-O-C bonds. During the sintering process of vitrified diamond composites, V2O5 film on the diamond surface dissolved in the vitrified bond, which would reduce the surface tension and refractoriness of vitrified bond at the interface and improve the wettability of vitrified bond to diamond. When the sintering temperature was at 650 degrees C, the flexural strength and Rockwell hardness of the diamond composites coated with V2O5 film were 92.8 MPa and 99.4 HRB, which are about 8.4% and 13.5% higher than those of the uncoated composites at 85.6 MPa and 87.6 HRB, respectively.