AZ31 magnesium alloy is processed by Ndglass laser with the wavelength of 1064 nm and pulse width of 23 ns. Optical microscope (OM) and transmission electron microscope (TEM) show that ultrahigh strain rate plastic deformation induced by laser shock wave takes place at the surface layer and results in extensive formation of dislocations and twins. High density dislocations tangle and intersect with twins lead to the refinement of grains. The micro-hardness of surface layer induced by laser shock processing increases by up to 58 % and the compressive residual stress on the surface of laser shocked area reaches up to 120 MPa. The corrosion behavior of AZ31 in 3.5% NaCl solution is investigated using potentiodynamic scanning technique and the slow strain rate test (strain rate up to 1×10-6). The experimental results show that the corrosion resistance of AZ31 magnesium alloy by laser shock processing reduces due to the rise of the corrosion potential and the increment of corrosion current. However, the stress corrosion resistance of magnesium alloy after laser shock is improved greatly.