Abstract: The spherical reciprocating friction and wear method was used under high-temperature conditions to study the effect of temperature on the friction and wear mechanism and microstructure of AISI 4340 low alloy high strength steel. The results show that the friction coefficient increases first and then decreases with increasing temperature, and the friction rate decreases first and then increases with increasing temperature. The surface of the wear scar was characterized by grinding traces with different morphologies, scale-like and granular abrasive debris. The surface of the wear scar and its subsurface layer have obvious plastic deformation. Under high-temperature conditions, the higher the ambient temperature, the larger the surface friction coefficient, the higher the surface roughness, the more obvious the grain refining phenomenon, the higher the hardness, and the better the wear resistance. When the temperature is low, the wear mechanism is mainly abrasive wear and adhesive wear, and when the temperature is high, it is a combination of abrasive wear, adhesive wear and fatigue spalling.