Abstract: We studied community structure and species diversity of mixed forests of deciduous broadleaved tree and Korean pine (Pinus koraiensis) in Mt. Changbai, Mt. Xiaoxing’anling and Mt. Zhangguangcailing, Northeast China. A total of 137 species belonging to 98 genera in 53 families were recorded in the nine plots. TWINSPAN analysis of the plots identified nine plots into four community types and three groups, while the 27 tree species established seven community types. Characteristics of community structure differed greatly among the 19 plots, which may be related to environmental factors, location and age of the community. Mean DBH decreased with the increase of stem density in accordance with a power-law function. There were significant correlations among the parameters of community structure. However, tree species richness did not correlate significantly with community structure. Concerning comparison among different layers, diversity (H′) and evenness (E) of herbaceous plants were the greatest, followed by those of shrubs and trees. The mixed forests of Mt. Changbai had the highest species richness, due mainly to a high richness of herbaceous plants and shrubs in Mt. Changbai.