Objective To improve the surface hardness and corrosion resistance of the Ti-6Al-4V in reducing acid solution by plasma surface zirconium alloying. Methods The chemical composition, phase structure and micro-hardness of the Zr-alloyed layer obtained at 800 ℃ , 850 ℃ and 900 ℃ were studied. The electrochemical behaviors of alloyed and untreated matrix in 10 % H₂SO₄ solution were also studied. Results The alloyed layers formed at three different temperatures exhibited a gradient composition and mainly consisted of α( Ti, Zr) and β( Ti, Zr) . The surface roughness of Zr-alloyed alloy increased with alloying temperature. The hardness of the alloyed layer was increased by about 200HV0. 1 compared with untreated Ti-6Al-4V and was gradually decreased along the alloyed depth. The corrosion potential of the alloyed layer shifted markedly to positive direction in contrast to the untreated matrix, while the passivation current density was decreased. Conclusion The micro-hardness and the corrosion resistance of Zr-alloyed Ti-6Al-4V were improved compared with the untreated titanium alloy. Among the temperatures tested, the corrosion resistance of the alloyed layer treated at 900 ℃ was the best, followed by the alloyed layer treated at 800 ℃ and 850 ℃