This experiment was carried out at the field in Guanwu Forest Station of Hsinchu Forest District Office. The purposes of this study are using the stand thinning operation of Taiwan Sassafras to create an open environment to investigate the effect of this thinning method would induce the seeds germination and seedlings sprout. After thinning the stand, the irradiation energy, the red/farred light ratio and the soil temperature on forest floor are increased significantly. This environment changes after thinning the stand may induce the seed germination and seedling sprout from seed or seedling bank in soil. As the results of this study, using the thinning method to reach the stand regeneration by seeds of the Taiwan Sassafras forest should have a high possibility.