Abstract: The pitting corrosion of the fresh stainless steel surface have been studied. The pitting critical potential of the fresh surface is lower than that of the surface covered by passive film. The pits on the fresh surface are primarily formed on grain boundaries and on inclusions. The morphology of pits are sharp streak pattern. According to the model of reaction steps of bare surface with chloride medium proposed by authors,the cours in which pits are formed on bare surface and the meaning of pit characteristic potentials have been discussed.