To investigate the population structure and community characteristics of Acer pentaphyllum, a plant species with extremely small populations, this study clarifies its resource status, identifies the causes of species endangerment, and provides a scientific basis for optimizing conservation strategies. In this work, eight representative and concentrated A. pentaphyllum communities in the Yalong River Basin were selected as research objects (located in Muhui Village, Luke Village, Rigang Village, Riga Village, Yageng Village, Diaoqiao Village, shady slope of Diaoqiao Village, and Nianjingfang Village, respectively), and the population structure, community diversity characteristics and soil chemical properties of these objects were investigated using a typical sampling method. The correlation between the three indices was explored through Pearson test, and the effects of soil properties on the diversity characteristics of A. pentaphyllum communities were evaluated using linear mixed effects models (LMMs). The results showed that: (1) The population size of A. pentaphyllum showed a "reversed J type" structure, with the highest proportion of individuals at level I accounting for 82.99% of the total population, and the survival curve of the population tended more towards the Deevey-Ⅲ type; (2) A total of 68 plant species belonging to 64 genera and 40 families were recorded. Leguminosae and Compositae had the highest species richness, followed by Labiatae, Rosaceae, and Polygonaceae; (3) The Simpson index, Shannon-Wiener index, and Patrick index were generally higher in the shrub layer than in the herb layer, and the highest values of all three indices across communities were consistently observed in the Rigang Village community; (4) The Sorensen index of different A. pentaphyllum communities ranges from 0.355 to 0.826, with the highest proportion of relatively similar performance among different communities; (5) There is a significant correlation (P<0.05) between soil moisture content and organic matter content with both the number of class I individuals and community diversity indices; (6) The R² decomposition of the marginal effects of LMMs indicates that soil moisture content and organic matter content have relatively high explanatory variance for the diversity characteristics of the shrub layer community, while organic matter and total nitrogen content have relatively high explanatory variance for the diversity characteristics of the herb layer. Thus, the size structure of A. pentaphyllum population in the dry-hot valley of the Yalong River exhibited a growing trend, but communities were characterized by low species richness, simple species composition, and high inter-community species similarity. Conservation efforts should prioritize the holistic protection of the community habitat, improving soil environmental management to enhance population and community stability.