Abstract: Tilia amurensis is an important broadleaved tree species in mixed broadleaved-Korean forests in northeastern China. In this study, the above-and belowground biomass allocation patterns of T. amurensis were analyzed using 39 harvested trees with different diameters at the breast height (DBH). And these trees were grouped into three size classes: small trees(1 cmDBH 10 cm), medium trees (10 cm DBH 20 cm) and big trees(DBH20 cm). Allometric equations for different biomass components were developed by stem diameters (DBH; tree base, DB; 30 cm height, D30 and 1 m height, D100). Our results showed that: 1) the relative proportions of stem and root biomass increased gradually at the small-and medium-tree classes, and decreased gradually at the big tree class. The proportion of branch and leaf biomass was just opposite. But no significant difference was found among different tree- size classes. 2) The branch and leaf biomass located mainly in middle and bottom layers of tree crown at each tree size category. 3 ) The aboveground biomass was significantly linearly correlated with belowground biomass(P 0.001). The slope of the fitted linear model was 0.31. 4) Both DBH and tree height showed a significant exponential correlation with aboveground competition intensity(P 0.001). There were no significant relationships between competition intensity and crown ratio, stem to foliage biomass ratio and root to shoot ratio ( P 0.05). But the ratio of tree height to DBH exhibited a significant power relationship with competition intensity(P 0.05). 5) According to the explainable variability and the significance of coefficients in allometric models, it can be concluded that DBH is a reliable variable for estimating the above-and belowground biomass of T. amurensis. Thus, the growth stage and tree size should be involved in allometry for precise estimation of above-and belowground component biomass.