Abstract: Low cycle fatigue test was conducted on P92 steel with RPL50 dynamic creep tester at 630 ℃ and different strain amplitudes, and the high temperature low cycle fatigue behavior of P92 steel was studied. Based on the relationship between plastic strain energy density and hardness, stress amplitude and low cycle fatigue life, low cycle fatigue life of P92 steel was predicted by energy-based hardness method, and compared with the test results. The results show that P92 steel was a cyclic softening material. The initial normalized stress amplitude increased with the increase of strain amplitudes, and stress amplitude decreased with the increase of cycles at different strain amplitudes. With the increase of strain amplitude, the elastic strain amplitude remained stable; the plastic strain amplitude increased approximately linearly; softening rate increased and was stable at about 0.3 finally. There was a good linear relationship between hardness and strain amplitude. The energy-based hardness method could accurately predict the high temperature low cycle fatigue life of P92 steel at 630 ℃, and the calculated predicted lives were all within ±1.5 times standard deviation of test lives.