Abstract. For the modified 3 16L stainless steel in which the dislocation interaction governs the fatigue hardening process, the high-cycle fatigue tests were carried out between 300 and 403 K. The in situ irradiation tests and the in situ thermal-pulse tests indicate that dislocation rearrangements due to thermal-pulse give rise to an increase in the areal density of persistent slip bands (PSBs), resulting in elongation of the fatigue life Nfi and an introduction of obstacles to dislocation motions, irradiation induced lattice defects or the fatigue induced precipitates, brings about a decrease in the areal density of PSBs, giving shortening of Nf