Abstract: The behavior of graphite phase in the laser hardening layer of gray iron is deeply studied by means of optical microscope and electron probe.Results show that the graphite dissolves completely and diffuses uniformly in the melt layer;the graphite in the phase transformation hardening layer dissolves partly,but the diffusion isn't uniformity;and that the graphite in the transition layer does not dissolve basically. It can be concluded that the behavior of graphite has close relation with the hardening layer structure and the effect of hardening.