Abstract: 128 trees of Pinus kesiya var. langbianensis were taken from the natural forests in Pu'er city of Yunnan Province as samples, the mingling (M), uniform angle index (W) and neighborhood comparison (U) were selected to describe the spatial structures quantitatively. The spatial structure indices for different components, and the relationship between the indices and the different components of above-ground biomass and their allocation proportions were analyzed using co-variance analysis and variance analysis. The results showed that: ① P. kesiya var. langbianensis is the single dominant tree species in the natural forests, it tends to an even spatial distribution, and the mixed patterns are from weak to moderate mixed. ② With the increase of the neighborhood comparison (U), the above-ground biomass value decreases, and the biomass proportion of wood decreases by the increasing biomass of bark, branches and needles. ③ For the relationship between above-ground biomass and the mingling (M), the biomass of all components reaches the maximum as the mingling (M) being 0.75, and the proportion of wood biomass takes up the highest value. ④ The effect of spatial distribution pattern on aboveground biomass and their allocation are not significant.