The effect of alternating current (AC) voltage of 0V, 1V, 3V, and 5V on magnesium alloy sacrificial anode electrochemical properties was studied by open circuit potential (OCP) analysis, electrochemical impedance spectroscopy (EIS), and polarization curve measurements. The results demonstrate that the AC voltage has a great effect on the magnesium alloy sacrificial anode. The corrosion control is anode control in the first two days with no AC interference. The stray current accelerates the transmission and diffusion of oxygen, so the corrosion rate under AC interference is higher than that with no AC interference. And the corrosion control becomes cathodic control under AC interference. The corrosion rate of the sacrificial anode is faster and faster as the AC interference voltage increases in the range of 0~5V, while the corrosion inclination is weakened.