Abstract: Creep experiments were conducted on plain and double-notched specimens of P92 steel under conditions of 650℃ and 120-145 MPa. Based on Liu-Murakami and Norton-Bailey constitutive models, a modified creep constitutive model was built and verified. On this basis, the determination method of model constants was confirmed, and the creep behaviors for the plain and double-notched specimens of P92 steel were simulated. The results show that the modified model was able to simulate the three stages of creep process at 650℃ of P92 steel, and reduced the problem of mesh-sensitivity of the conventional Kachanov-Robotnov (K-R) model. The creep frature life of the double-notched specimen was longer than that of the plain specimen under the same condition, namely the notch strengthening effect. And with the increase of the notch acuity ratio, the strengthening effect became more obvious. The damage quantity had a positive correlation with the multiaxiality.