Studying community assembly through the integration of functional and phylogenetic diversity can elucidate the ecological selection strategies, spatial distribution patterns, and mechanisms of diversity maintenance in plant communities. Additionally, investigating the mechanisms of plant community assembly in mountainous regions can aid in the conservation of plant resources and the ecological environment in these areas. Most previous studies have focused on combining species diversity and phylogenetic diversity to reveal community assembly mechanisms, while fewer studies have explored community assembly based on functional and phylogenetic diversity. In this study, the plant communities at varying altitudes in the Beishan mountains of Kuqa were used as the research object. The research analyzed the patterns of phylogenetic and functional diversity across different altitude gradients, using a combination of functional traits and phylogenetic information. Screening environmental factors that influence phylogenetic and functional diversity, thereby elucidating the mechanisms of plant community diversity maintenance and its driving factors in the Beishan mountains of Kuqa. The results of the study showed : (1) The functional richness index (FRic) and functional evenness index (FEve) exhibit a "single-peak" pattern with increasing altitude, reaching their highest values at 2300 m above sea level; The Functional Dispersion Index (FDis) exhibited a "unimodal" trend, initially decreasing and then increasing with altitude, with the highest value observed at 3100 m above sea level; The Rao Quadratic Entropy Index (Rao,Q) showed a monotonic decrease with increasing altitude. The phylogenetic diversity index (PD) exhibit a "single-peak" pattern, initially increasing and then decreasing with altitude. The phylogenetic structure index transitioned from a state of dispersion to a state of aggregation. Overall, competitive exclusion was the primary mechanism driving the assembly of low-altitude communities, whereas habitat filtering was the dominant factor influencing the construction of high-altitude communities. (2) The phylogenetic signal K values of species functional trait indicators in the plant communities of the study area showed that, except for plant height, the K values for all other traits were less than 1. This indicates that environmental heterogeneity has a stronger influence on the functional traits of plant communities than evolutionary history. (3) The results of redundancy analysis indicate that altitude is the primary factor influencing the distribution of plant communities in the Beishan mountains of Kuqa, followed by mean annual temperature, soil quick potassium, soil ammonium nitrogen, and soil water content. Stepwise regression analysis further revealed that mean annual temperature significantly influenced the phylogenetic diversity index (PD) and the net relatedness index (NRI). The net taxonomic index (NTI) was primarily affected by altitude and nitrate nitrogen. Functional trait diversity indices were influenced by altitude, soil nitrogen and phosphorus, as well as soil water content.