The effect of Er content on microstructure of Al-Zn-In alloy anodes were studied by using scanning electron microscopy(SEM), energy spectrum analysis and X-ray diffraction analysis. The polarization curves and EIS of Al-Zn-In alloy with different Er content were tested in the 3.5wt% NaCl solution. The results show that with the increase of Er content, the dendrite was refined, the amount of inter-dendritic precipitates increased, the corrosion potential became more positive, the radius of electrochemical impedance spectroscopy enlarged and corrosion rate also decreased. Al-5Zn-0.03In-1Er alloy has refined dendrites and proper amount of precipitates, with the corrision morphologies of independent pitting, corrosion in uniformity, which is an ideal choice for using as sacrifical alloy.