Abstract: The high-cycle fatigue（HCF） experiments of 6XN stainless steel and alloy 825 were conducted under bending and rotating loads at room temperature（RT） as well as at 550℃ in air.The results indicate that the fatigue limited stress of 6XN at RT is higher than that of 825,which consistent with the order of their tensile strength.The oxidation rate of the specimen increased at 550℃,therefore the fatigue life of the specimen decreased,among them 6XN was more sensitive to high temperature with the larger decreasing tendency which make the fatigue limited stresses of the two alloys more closer at 550℃.While 825 is more sensitive to the stress cycles,both materials have good resistance to high cycle fatigue when comparing their experimental data with the calculated value from the empirical formula.The fracture morphology presents the areas of crack initiation,crack growth and fracture,and the fracture area has much dimples.