Biodiversity patterns and their underlying mechanisms have long been focal topics of study for ecologists and biogeographers. However, compared with spatial variation in species richness (α- and γ-diversity), β-diversity, or the dissimilarity of species composition between two or more sites has until recently received limited attention. In this study, we explored the large-scale patterns of altitudinal turnover (β-diversity) of plants in montane forests of China, based on systematic inventories of 1153 plots from 46 mountains distributed over ˜30 degrees of latitude (21.9–51.7°N) and ˜4100 m of altitude (160–4250 m). The β-diversity of trees and shrubs declined significantly with increasing latitude. Along the altitudinal gradient, β-diversity of both trees and shrubs showed non-significant trends in most mountains. Differences in climate explained ˜30.0% of the variation in tree β-diversity (27.7, 36.5, and 26.2% for the Jaccard's, βj, Sorenson's, βs, and Simpson's dissimilarity, βsim, respectively), with mean annual temperature being most important, and ≤ 10.0% of that in shrub β-diversity (10.0, 8.2, and 7.0% for βj, βs, and βsim, respectively), with annual actual evapotranspiration and annual precipitation as the main predictors. However, climatic controls of β-diversity varied dramatically in different biogeograpical regions. The β-diversity of trees exhibited stronger, whereas that of shrubs showed weaker, climatic patterns in temperate and arid than subtropical regions. These results suggest that mechanisms causing patterns of β-diversity may differ between latitudinal and altitudinal gradients, and among biogeographical regions; as a result, caution should be exercised in drawing close parallels between patterns and causes of β-diversity along latitudinal and altitudinal gradients and among regions.