Molecular dynamic simulation is performed to study the process of material annealing caused by a 266 nm pulsed laser. A micro-mechanism describing behaviors of silicon and impurity atoms during the laser annealing at a non-melt regime is proposed. After ion implantation, the surface of the Si wafer is acted by a high energy laser pulse, which loosens the material and partially frees both Si and impurity atoms. While the residual laser energy is absorbed by valence electrons, these atoms are recoiled and relocated to finally form a crystal. Energyrelated movement behavior is observed by using the molecular dynamic method. The non-melt laser anneal appears to be quite sensitive to the energy density of the laser, as a small excess energy may causes a significant impurity diffusion. Such a result is also supported by our laser anneal experiment. Molecular dynamic simulation is performed to study the process of material annealing caused by a 266 nm pulsed laser. A micro-mechanism describing behaviors of silicon and impurity atoms during the laser annealing at a non-melt regime is proposed. of the Si wafer is acted by a high energy laser pulse, which loosens the material and partially frees both Si and impurity atoms. While the residual laser energy is absorbed by the valence electrons, these atoms are recoiled and relocated to finally form a crystal. The movement behavior is observed by using the molecular dynamic method. The non-melt laser anneal appears to be quite sensitive to the energy density of the laser, as a small excess energy may cause a significant impurity diffusion. Such a result is also supported by our laser anneal experiment.