Abstract: In this paper, cyclic stress-strain behavior for an iron-ba-sed supera-lloy GH36 under combined creep and fatigue at 550℃ was investigated. The experimental results are preliminarily studied. Analysis indicates that the main reason for the dec-rease in failure life with holding time at maximum tensile strain is the increase in creep strain and creep-fatigue interaction, and its microscopic mechanism is that fatigue crack joins the "W" type or "R" type intergranular creep damage.