In order to study the influence of warm laser peening on the thermal relaxation behavior of Inconel718 superalloy, the LP(20℃) IN718 and WLP(260℃) IN718 are served as the research objects. From the view points of microstructure and residual stress, the relationship between temperature, time and residual stress are explored by experiments. The thermal relaxation behavior of residual stress are analyzed from the perspective of material softening and creep-controlled behavior at elevated temperature. The results show that the WLP(260℃) IN718 superalloy has a better performance in residual stress stability, grain size and dislocation density compared with LP(20℃) IN718; the relaxation amplitude increases with the increase of applied temperature, and the thermal stability and dislocation density of residual stress in LP(20℃)IN718 is better than that in WLP(260℃) IN718; the maximum rate of stress relaxation take place at the initial stage of peening process in all conditions, the LP(20℃) and WLP(260℃) surface residual stress have released 68% and 36.7% respectively after exposed 500min at 700℃. Thermal relaxation behavior can be described by Zener–Wert–Avrami function.