TiO2 coatings on titanium alloy substrates were prepared by atmospheric plasma spraying using commercial nano-powders and followed by H2SO4 treatment. The bioactivity of coatings was evaluated by the simulated body fluid soaking test. Scanning electron microscopy and energy-dispersive X-ray spectrometry were used to characterize the surface morphologies and phase composition of the coating before and after soaking in simulated body fluid. The results obtained indicate that H2SO4-treated TiO2 coating can induce a bone-like apatite formation on its surface, however, no apatite appears on the surface of as-sprayed TiO2 coatings. The acid concentration and treated time affected the bioactivities of TiO2 coatings.