The effect of laser shock processing (LSP) on electrochemical corrosion behavior of AZ91 magnesium alloy in NaCl solution of mass fraction of 3.5% is studied by using electrochemical technique and transmission electron microscopy. The results show that a lot of dislocations reduce in the alloy after LSP. Impedance of AZ91 magnesium alloy increases significantly and the electric current density reduces significantly after LSP. With the impact times of LSP increasing, the self-corrosion potential of AZ91 Mg alloy begin to move towards a positive direction, the corrosion current destiny declins while the corrosion resistance is improved in 3.5% NaCl solution.