Based on density decision model of plantation established by continuous stages dynamic programming, Genetic Algorithm is presented to select optimal decision in determining thinning age, and cutting age during stand management.The mathematical models and concrete method are offered and discussed.The density optimal projection of Chinese fir plantation during its management shows that Genetic Algorithm can get satisfactory results.The optimized results indicate that the optimal frequency of thinning is 2 for Chinese fir plantation during its management. The first time for thinning can be 11～12 years, while the second time for thinning can be 15～18 years. The optimal time for final cutting is 25 years.