Abstract: 【Objective】In this study，the relationship between DBH and height，height below branch，component biomass was studied by taking the natural sympodial bamboo (Dendrocalamus tsiangii) in Libo County as the research object. The variation rule of bamboo inter length and the distribution pattern of aboveground biomass were studied，aiming to further enrich the research results of biological characteristics of this bamboo species and provide reference for biomass estimate and sustainable management of D. tsiangii. 【Method】 Using random sampling method to determine the biomass of the aboveground part and the water content of each component. 【Result】 The results showed that the correlation between the DBH and height of D. tsiangii，as well as the total biomass of culms, branches，leaves，and aboveground parts，fitted by multiple models，reached a highly significant level. The bamboo internode length showed the distribution law of ‘short—long—short’，and the bamboo culms whose internode length is 30-40 cm occupied 32% of the total. The aboveground biomass of the bamboo culms accounted for the largest proportion of the total，which reached 85.52%. The average water content of each component is decreasing in the trend of culm > branch > leaf，and gradually decreases with the increase of age class. The optimal growth models for DBH and total aboveground biomass，as well as biomass of bamboo culms，branches，and leaves，are as follows：W_total=0.372D²-0.753D+1.316 (R²=0.897)，W_culm=0.343D²-0.875D+1.311 (R²=0.891)，W_branch=0.047e^0.560D (R²=0.479)、W_leaf=0.079e^0.469D (R²=0.622)，the research provided a theoretical basis for scientific management of D. tsiangii. 【Conclusion】 This paper has enriched the biological characteristics research of D. tsiangii forest to some degree，and proposed mathematical models for the diameter at breast height，total aboveground biomass，and biomass of each component of this bamboo species，which has provided a scientific basis for accurately estimating the biomass of the bamboo forests.