Abstract: This paper investigated high temperature HCF, static and dynamic creep behaviours in GH33A superalloys with and without Mg and Zr.HCF notch sensitivity in the two alloys was analysed.Results show that a small amount of Mg and Zr can improve neither HCF properties nor fatigue notch sensitivity. Notch fatigue limit depends on smooth fatigue limit, grain size and notch geometric parameters Kt and λ (stress concentration coeffecient and stress gradient).A small amount of Mg and Zr can intensively prolong secondary creep stage and well develop tertiary creep stage, and so increase stress rupture life and stress rupture ductility significantly.The benificial effect still exists under dynamic creep condition.