Abstract: The underground and aboveground standing biomass and productivity of Populus×xiaohei plantation with different densities and stand ages were measured by the methods of sampling typical plot and allometric dimension analysis in Xuejiazhuang Forest Farm in Shanxi Province. It showed that the rationale density of Populus×xiaohei plantation was 500 trees per hectare. The biomass of 29 years old Populus×xiaohei plantation with 1 000, 500, 250 trees per hectare was 85.31 t·hm-2, 102.60 t·hm-2, and 86.74 t·hm-2, respectively. The productivity of Populus×xiaohei plantation was 3.16 t·hm-2·a-1, 3.80 t·hm-2·a-1, and 3.21 t·hm-2·a-1, respectively. The proportion of tissue biomass had little difference in the 29 years old stand. The proportion of aboveground biomass ranged from 83％ to 86％, the proportion of stem ranged from 57％ to 62％,the branch ranged from 11％ to 16％,the leaf ranged from 2％ to 3％,and the bark ranged from 8％ to 10％;the proportion of underground biomass ranged from 14％ to 20％. The biomass and productivity of 27 years old Populus×xiaohei plantation was higher than the that of 23 years old Populus×xiaohei plantation. The biomass increased by 59.74% in 27 years old plantations, and productivity increased by 36.20%. The proportion of leaf and root in the 23 years old plantations was significantly higher than that of 27 years old plantations, but the proportion of stem biomass in the 23 years old plantations was lower than that of 27 years old plantation, which showed that the 23 years old plantation was in rapid growth period. Therefore, the rotation of Populus×xiaohei plantation should be longer than 27 years. There was a very significant correlation between the biomass of Populus×xiaohei and the canopy indexes. The relationship between tree stem biomass and tree canopy indexes could be described as y=ax+b. Applying remote sensing techniques in biomass estimation was practicable, and it could provide the basis data for remote sensing techniques in wood properties estimation.