Abstract: A model reflected the relationship between the basal area and the density of the plantation was derived by the analysis of their mutual funciion biologically as well as mathematically. Its characteristic form can be written as:S=Aρ^α in which-l ≤ a ≤-2/3,where S and ρ represent the basal area and the density respectively and A is a constant. The model was applied successfully in the spruce plantation at 20 ages. Moreveor, by resorting to the fuzzy set cluster analysis, the optimal plantation densities were concluded. The result showed that, under λ=0.79 level cutting, the spruce plantation densities should be controled between 2150~2550 No./hm² in order to achieve a sound management.