TiO2 films were prepared on the surface of diamond through sol-gel method. The effect of heat treatment temperature on morphology, phase composition, phase transition, bonding with diamond, and oxidation resistance of diamond coated with TiO2 films of TiO2 film of diamond surface were characterized through SEM, FTIR , Raman spectroscopy, X-ray diffraction analysis, XPS, TG-DSC, fracturing strength. The results showed that when the heat treatment temperature rose to 600℃, TiO2 film of diamond surface would change from amorphous state to a dense anatase films and Ti-O-C chemical bond was formed between TiO2 and diamond substrate. When the heat treatment temperature rose to 800℃, TiO2 film was still anatase phase, graphitization of diamond substrate generared, graphitization C could form Ti-O-C chemical bond with TiO2 film, however, TiO2 film began to emerge cracks. Meanwhile, the heat treatment temperature of TiO2 films had a greater impact on the oxidation resistance of diamond in the air. When the heat treatment temperature was at 600℃, diamond initial oxidation temperature reached a maximum 754 ℃.After diamond coated with TiO2 films oxidized at 800℃ for 0.5h in the air, the weight loss rate and compressive strength was 6.7wt.% and 15.7N, respectively.