Plant architecture, reflecting ecologically adaptive strategy of plants in response to changing environment, refers to the overall shape and size of the wood plants and the spatial arrangement of its components such as crowns, stems, branches and leaves. For mechanical and hydraulic reasons, architecture of a plant can greatly affect whole-plant function such as photosynthesis, transpiration and energy balance. As one of the leading dimensions in shaping plant function, plant architecture is also fundamental to influence species demographics, and consequently species coexistence. Therefore, variation in plant architecture among communities that differ in site properties is considered to indicate relationship between plant architecture and environmental stress. Linking spatial pattern of plant architecture with changes in altitude is important for understanding plant adaptive strategies in relation to biomass allocation. However, little is currently understood whether plant architectural traits correlate to the site properties with changing altitude in the evergreen broad-leaved forests. In this study, our objectives were to elucidate variation in plant architectural traits among communities, and to explain the mechanical relationships between plant architectural traits and environmental conditions. Specifically, three community types, i.e., Castanopsis fargesii community, Cyclobalanopsis gracilis community and Cyclobalanopsis sessilifolia community, differing in altitude, were selected in Taibai Mountain in Tiantong region, Zhejiang Province, to examine plant architectural traits including tree height, crown depth and area, leaf convergence, the lowest branch height (LBH) and basal diameter at the 45 cm aboveground (D₄₅). In addition, crown exposure index, soil moisture content, air humidity, air temperature, soil pH, and windy velocity in each of three communities were determined. Then variation in architectural traits for plants in each of tree and shrub layers among communities, and their relationships with environmental factors were analysized. The results shown that, for plants in shrub layer, plant height, crown depth, the lowest branch height and basal diameter at the 45 cm aboveground increased, but proportion of leaf convergence decreased gradually from Castanopsis fargesii to Cyclobalanopsis sessilifolia community with increasing altitude. However, for plants in tree layer, tree height, crown depth, crown area, LBH and D₄₅ decreased, while leaf convergence increased. Significant correlations among architectural traits (P<0.01) was found in three altitudinal communities for plants in shrub layer, but for plants in tree layer, architectural traits correlated significantly in the lowest and intermediate altitudinal communities only. Crown exposure index in both shrub and tree layers increased significantly from Castanopsis fargesii to Cyclobalanopsis sessilifolia community with increasing elevation (P < 0.05). Multiple stepwise regression demonstrated that, for plants in the shrub layer, crown exposure index was mainly responsible for variation in plant architecture, whereas, soil moisture content, wind velocity, and soil pH were the determinant factors influencing plant architecture for plants in the tree layer. In conclusion, plant architectural traits vary differently with community change for plants in each of shrub and tree layers in Taibai Mountain in Tiantong region. Variability of plant architecture in shrub layer results largely from light competition, while plant architecture in tree layer was driven by wind velocity and soil moisture content.