Abstract: The electrochemical behavior and discharge performance of AZ31 magnesium alloy in different concentration of Al(NO₃)₃ solution were investigated by the testing and analysis of hydrogen evolution, open circuit potential, potentiodynamic polarization curve, alternating current impedance and constant-current discharge performance. The results indicate that with the increase of concentration of Al(NO₃)₃ solution, the open circuit potential and the free corrosion potential shifted negatively, the alternating current impedance decreased and the electrochemical activity enhanced. Compared with magnesium salt solutions, AZ31 magnesium alloy had higher constant current discharge voltage, more stable discharge curve, higher discharge efficiency and larger discharge capacity in 0.6 mol·L^-1 Al(NO₃)₃ solution. 2Mg(OH)₂·Al(OH)₃ was generated on the surface of the AZ31 magnesium alloy electrode in the progress of discharge which promoted the Mg(OH)₂ to fall off from electrode surface easily and helped the electrolyte contact with the electrode surface. The AZ31 magnesium alloy electrode had high discharge activity and discharge stability.