Abstract: Low cycle fatigue (LCF) tests were conducted on N18 alloy at different temperatures varying from room temperature to 500 ℃.The results show that N18 alloys display cyclic softening from room temperature to 300 ℃. When the temperature is 400 and 450 ℃, the alloy presents the cyclic hardening gradually; at 450 ℃, its hardening phenomenon is more obvious. Saturation stage occupies the majority of the entire cycle fatigue life at 500 ℃. The fatigue life increases as the temperature increases, then the fatigue life decreases, LCF life shows a maximum at 300 ℃, and the temperature effect on life is more pronounced at low strain amplitudes. The analysis of the fracture surface reveals fatigue cracks originated in a single source at room temperature, on the fatigue crack propagation’s stage, micro-feature is mainly the fatigue stripe, and the local region presents the tire-like pattern. However, at high temperature, there are multiple crack sources, the fracture is characterized by secondary cracks.