Abstract:In six kinds of densities. above-ground biomass of six-year-old poplar plantation (Ⅰ-72/58)was compared on intensively cultured plots in Shan dong province. The average-sampling-tree method was used to estimate the biomass and the net production of the poplar plantation of different age The biomass yields of six-year-old poplar plantation ranged from 64 to 122 t/ha in six kinds of densities; The higher the density, the more biomss of plantation was. The greatest net production was 20 t/ha. yr. in higher planting density (1000 trees/ha) and some others were over 10 t/ha. The proportions of biomass composition. (stems, barks, branches and leaves) were respectively as follows: 60—70%: 10—12%: 12—21%: 3—5%. The yield of biomass was increasing rapidly after second year in each density plantation and it still kept the increasing tendency when they were investigated. Allometric method was used too. The results of above mentioned two methods were compared. The comparision showed that both ways to estimate the biomass of poplar (Ⅰ-72) plantation were suitable.