Abstract: YUS270 steel is a super austenitic stainless steel produced by Japan and has a perfect pitting resistance.The specimens had been put into the hydrochloric acid with FeCl₃ for testing pitting resistance.The experiment was based on ASTM G-48 Test Method C at 40℃. Then the losing weight, pitting density and maximal depth were compared. The results showed that all the items satisfied the standard in this condition. It also proved the excellent pitting resistance of Cl^-1 of YUS270 steel and provided the evidence for the application in the offshore oil platform.