The pitting behavior of 316L before and after explosive welding was studied with X-ray diffraction(XRD), scanning electron microcopy(SEM), optical microscope(OM), potentiodynamic polarization and immersion corrosion technology. XRD analysis indicates that the second phase and δ ferrite phase emerged on the side weld and fusion area of 316L relative to the sample of 316L base; The result of potentiodynamic polarization and immersion corrosion test indicates that 316L base and welded metal had passivity, but welded 316L pitting resistance was decreased and welded seam and fusion area were corroded firstly