The plant community is the product of the interaction between plants and the environment. The quantitative classification and ordination can objectively and accurately reveal the complex ecological relationships between plant communities and the environment. Exploring the distribution law of forest communities, the pattern of species diversity and its relationship with environmental factors is of great significance for protecting forest species and species diversity. Taibai Mountain Nature Reserve located in the middle of the Qinling Mountains is renowned for its abundant animals and plant resource as well as the obvious vertical zoning of vegetation. In view of superior environment for vegetation growth in the lower and middle altitude areas, there are undoubtedly more opportunities for the stable breed and survival of rich species. On account of the difficulty resulted from the complex species distribution in classifying communities, this study conducts sample plot survey of typical forest communities in the reserve, and attempts to carry out community classification research by combining multivariate regression tree (MRT) and canonical correspondence analysis (CCA). The discontinuity of classification and the continuity of ordination could be considered as the reasonable evidence to reveal the relationship between community distribution and the environment. Besides, the comparison of three overall diversity indexes in different communities and the further study regarding the change pattern of forest community diversity at altitude levels are of great significance to better reveal the change law of environmental gradients in the biodiversity of Taibai Mountain Nature Reserve. The results revealed that (1) the typical forest communities in Taibai Mountain Nature Reserve can be divided into 6 types through cross-validation after performing MRT classification on 30 plots. The specific parts are as follows: Ⅰ Quercus variabilis + Viburnum mongolicum + Anemone vitifolia, Ⅱ Pinus tabuliformis + Coriaria nepalensis + Lithospermum erythrorhizon, Ⅲ Pinus armandii + Bashania fargesii + Dryopteris rosthornii, Ⅳ Quercus aliena var. acutiserrata + Cerasus tomentosa + Sinacalia tangutica, Ⅴ Abies fargesii + Rhododendron purdomii + Ligularia sibirica, and Ⅵ Larix chinensis + Lonicera stephanocarpa + Deyeuxia arundinacea. (2) Based on the ordination of CCA, it not only can reveal the habitat distribution range of the community, but also the relationship between forest communities and environmental factors in Taibai Mountain Nature Reserve. Furthermore, studies indicated that four environmental factors including altitude, slope, litter thickness, as well as disturbance could exert significant effects on community distribution in the study area. The first sorting axis is mainly related to altitude. While the second sorting axis is mainly relevant to slope, litter thickness, and interference intensity. (3) The three diversity indexes of community IV are the highest, the species richness and Pielou evenness of community I are at the lowest level. Moreover, the Shannon-Wiener diversity index of community VI is the lowest. In addition, in terms of the aspect of altitude, the three total diversity index of communities located at middle altitude is usually higher,while there is a relatively low total diversity index of the communities located at high and low altitudes. This study aims at comprehensively and systematically exploring the division of forest communities, impact factors as well as community diversity patterns in the Taibai Mountain Nature Reserve, and meanwhile providing a theoretical basis for further understanding of the forest vegetation pattern and management and protection of forest resources in the Nature Reserve.