Abstract: The crack growth property under fatigue-creep interactions in nickel-base superalloy GH33A at 700 C is investigated with the alternate electric potential technique.The fracture feature is analyzed with optical microscopes and SEM. It is shown that the fatigue-creep interactions accelerate the crack prowth, and log（da/dN） varies with log（ K）in accordance with the broken line rule. As indicated by experiwents, it is possible to use the elastic -plastic fracture mechanics parameter C*as the criterion of the crack growth under fatigue-creep interaction.The equation of crack growth rate is （da/dN） = 6.00×10-2C*0.78Fatigue-creep interactions cause intergranular growth to appear, and both the link of main crack with W type micro-crack and the shearing fracture along the sliping plane are two main micro-mechanisms of fatigue-creep interactions.