Abstract: Low cycle fatigue tests of N80Q steel for oil well casing were carried out on Instron 8862 fatigue tester under complete symmetrical cycle loads (mean strain of 0) and non-symmetrical cycle loads (mean strain of 0.5% and 1.0%). The low cycle fatigue characteristics of the steel were studied, and the prediction accuracy of low cycle fatigue life models considering different factors was discussed. The results show that the plastic strain energy increased linearly with increasing strain amplitude, and the mean strain had little effect on the plastic strain energy. There was no stress relaxation behavior of N80Q steel under different strain amplitudes (0.5%-2.0%) and symmetric load or under strain amplitude greater than 1.0% and asymmetric load. When the strain amplitude was less than 1.0% under asymmetric load, the stress relaxation behavior was obvious; the larger the initial mean stress, the more obvious the stress relaxation behavior. The empirical model considering the influence of maximum stress, stress range, strain range and mean strain had higher prediction accuracy, and the predicted lives were mainly dispered in 1.2 time scatter band.