Abstract: The sample plots of 28-aged Pine plantation (Pinus tabulaeformis) were located on the southern and northern slope of Xishan (West Mountain) at an altitude of 300--350m. By using power equations W(stem weight)= 2.372 (D2H)0.664,W(branches weight)= 1.317 (D2H)0.992,W(leaves weight) = 1.417(D2H)0.833, and W(roots weight)= 1.593 (D2H)0.757, the biomass of stems, branches, leaves and roots was obtained. The biomass of tree layer of Pine plantation on the southern and northern slope was 29.13t/ha, 42.46t/ha respectively. By using direct harvest method to estimate the seasonal dynamic of shrub and herbaceous layers in Pine plantation, the biomass of the shrub layer on the southern and northern slope in August was 8.05t /ha and 5.78t/ha, the biomass of the herbaceous layer was 0.74t/ha and 0.77t/ha respectively. The total biomass of the Pine plantation on southern and northern slope was 38.08t/ha and 48.68t/ha respectively.