The hydroxyapatite (HA) coating, one of the most important biomaterials, was prepared on Ti6Al4V alloy by Mg sacrificial anode to improve the anticorrosion electrochemical characteristics. Energy dispersive X-ray analysis (EDX), electron probe microanalyzer (EPMA), Fourier transform infrared spectra (FTIR) and X-ray diffraction (XRD) were used to analyze the HA coating. The results show that the HA coating is composed of needle-like hydroxyapatite crystals with the Ca/P ratio of 1.4063. After the immersion test of 30 d, the crystals become larger in Hank’s solution, from needle-like to sheet-like in Ringer’s solution and column-like in Tyrode’s solution. The tests of open circuit potential, polarizing curves and EIS method in Hank’s solution, Ringer’s solution, Tyrode’s solution and human blood show that the Ti6Al4V alloy with HA coating has better electrochemical characters than Ti6Al4V alloy