Abstract: The surface of X70 pipeline steel welded line was treated by laser shock wave, and the corrosion performances before and after laser shock processing were analyzed by salt spray corrosion test in artificial atmosphere.The surface morphologies, chemical elements and phase constituent were observed with SEM(scanning electron microscope), EDS(energy dispersive spectrometer) and XRD(X-ray diffraction), respectively, and the effects of laser shock processing on the corrosion mechanism were discussed.The results show that tensile residual stress exists in the surface of X70 pipeline steel welded lines in primitive state, which improves stress corrosion crack with the interaction of corrosive medium Cl^-.Spelling corrosion occurs with the interaction of boundary corrosion.The grain refinements are produced in the welded lines by laser shock processing, and the strengthened layer is formed on the surface, which improves corrosion resistance of the welded lines.