We have reproduced columnar grains formed after laser crystallization from amorphous-Si to poly-Si in actual experiments using a crystallization simulator. The crystallization simulator possesses random nucleation, crystal growth velocity, latent heat emission, and partial crystallization models. The columnar grains appear by assuming partial melting condition where thin amorphous-Si remains underneath and that the nucleation rate at the interface between the amorphous-Si and liquid-Si is larger than 5 x 10(18) cm(-2) s(-1). The nucleation rate corresponds to that the nucleation probability at the interface is more than five times as large as that inside the liquid-Si. (c) 2012 Elsevier Ltd. All rights reserved.