Abstract: The corrosion behavior of 5083 aluminum magnesium alloy in NaCl solution at different concentrations was studied by polarization curve method and AC impedance spectroscopy in scanning electrochemical microscopy (SECM). The results show that the corrosion of alloy is neutralized in neutral NaCl solution. With the increase of salinity, the damage of Cl^- to the alloy matrix is aggravated. The corrosion potential is positive and the pitting potential is decreased. The electrochemical impedance spectroscopy is only 1 capacitive arc, showing a contraction trend. At the same time, the impedance decreases, the phase angle increases, the dispersion index decreases, and the corrosion resistance of the alloy decreases. The strong activation of Cl^- in the solution, will damage the alloy surface oxide film, gradually replacing the OH^- in corrosion products of Al (OH)₃ and formation of new corrosion products of AlCl₃.