The study of phylogeny and the functional trait structure of plant communities is useful for understanding the maintenance mechanism of plant diversity and the relation between species. The geographical environment of Gansu Province is complex. The remarkable and changeable climate gradient has formed regional vegetation and environmental differences, enriched habitat types, and has significant vertical connectivity and latitude isolation. Taking typical plant community of latitude gradient in Gansu Province as the research object, through community investigation and functional traits determination, the net relatedness index (NRI) and mean paired trait distance (PW) were calculated to analyze the response of plant community phylogenetic structure and functional trait pattern to different latitudes. The results showed that:(1) Shannon-Weiner diversity index, species richness, and phylogenetic alpha diversity index presented a significant decrease trend with the increase of latitude (P<0.05), while the Pielou evenness index had no significant change trend with the increase of latitude. (2) The phylogenetic structure tended to be divergent at high and low latitudes (NRI<0), and then showed a spectral structure of aggregation at mid-latitudes (NRI>0). It indicates that interspecific competition weakens, environmental filtering gradually increases, and similarity limitation prevails in the process of species aggregation as latitude continues to increase. However, the functional trait structure of the community showed the opposite of the spectral structure as latitude increased, so the phylogenetic and functional trait structures of the plant community are not consistent. (3) Plant height showed weak phylogenetic signals (P<0.05) and other traits showed no significantly phylogenetic signals, indicating that plant functional traits were greatly affected by environmental factors and had little relationship with phylogeny. In general, the maintenance mechanism of species diversity of typical latitude gradient plant community in Gansu Province was dominated by a deterministic process, which supported the ecological niche theory. Among them, environmental filtering and competitive exclusion played a dominant role in the process of species aggregation in most communities. Environmental factors such as soil moisture content, soil pH, and mean annual temperature had a significant impact on the pattern of plant traits. This study contributes to understanding of the geographic distribution patterns and potential ecological maintenance mechanisms of plant diversity in different climatic zones.