This study systematically investigates the influence of temperature on the low-cycle fatigue （LCF） deformation mechanisms of the fourth-generation powder metallurgy （PM） superalloy FGH4108. Strain-controlled fatigue tests were conducted at temperatures ranging from 400 ℃ to 850 ℃， in combination with microstructural characterization techniques including scanning electron microscopy （SEM）， electron backscatter diffraction （EBSD）， and transmission electron microscopy （TEM）. The evolution of the fatigue response from cyclic hardening to softening under temperature control was elucidated. The results show that FGH4108 exhibits significant cyclic hardening behavior at temperatures up to 600 ℃， whereas cyclic softening becomes dominant above 700 ℃， with the most pronounced effect observed at 850 ℃. Fracture mode transitions from transgranular to intergranular with increasing temperature， accompanied by a change in deformation mechanism from dislocation accumulation in the matrix to a combined mechanism of γ′ precipitate shearing， stacking fault formation， and twinning. TEM observations revealed that the γ′ phase exhibits reduced thermal stability at elevated temperatures， with localized stacking faults and γ′ shearing features observed. EBSD analysis indicated that the distribution of intragranular local misorientation remains relatively stable between 600 ℃ and 850 ℃， suggesting a limited influence of temperature on overall dislocation density. These findings provide insights into the temperature-dependent fatigue behavior of FGH4108 and offer theoretical guidance for performance evaluation and design optimization of next-generation PM superalloys.