The composite consists of disordered and ordered iron platinum (FePt) alloys was induced by nanosecond pulsed laser (NPL) irradiation. The process was investigated by laser high-voltage electron microscopy (laser-HVEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD) analyses. The structural transformation upon NPL irradiation was monitored by laser-HVEM imaging, with the structure being modified in a short second after the one pulse. XRD analyses revealed expanded and contracted lattice distances before and after NPL irradiation, respectively. According to the XRD and TEM results, the surface of FePt alloys was transformed from fct to fcc structure with structural strain by NPL irradiation.