Stress corrosion studies of 50 Mn18Cr4 austenitic steel implanted with 120 keV N+, 100 keV Cr+, 200 keV and 400 keV Er+ ions were carried out by constant strain method in the nitrate solution. Surface composition and depth profiles of the implanted material were measured by AES sputter etching technique. The results exhibit that nitrogen implantation has no significant affection to the stress corrosion, but the chromium and erbium implantation has prolonged the incubation period of the stress corrosion cracking.