Abstract: The pitting corrosion resistance of martensitic stainless steels 0Cr17Ni4Cu4Nb treated separately with solid solution + aging and solid solution +adiustment+ aging was investigated in concentrated chloride media by chemical immersion and simulated occluded corrosion cell(OCC)test in comparison with that of 18-8 type austenitic stainless steel(316L).The results show that rich Cu precipitation phases in the martensile promote corrosion pit initiation,and the development of the pit depends on.organization morphology.For 0Cr17Ni4Cu4Nb martensitic stainless steel treated with solid solution +adiustment +aging,rich Cu precipitation phases are more and biger and the martensita lath is fine,the pits are more dense with size and depth smaller,while for 0Cr17Ni4Cu4Nb martensitic stainless steel treated with solid solution + aging,are less and smaller and the martensite lath is coarse,the pits are less dense with size and depth bigger.With pitting corrosion resistant of 18-8 type austenitic stainless steel comparison,it shows that the pitting corrosion resistance of 0Cr17Ni4Cu4Nb martensitic stainless steel is as good as 18-8 type austenitic stainless steel,if heat treated properly.