[Objective] The relationships between vegetation communities and soil environmental factors on highway slopes were examined in order to reveal vegetation-soil feedback mechanisms. [Methods] Four typical plant community sample plots labeled A, B, C, and D were established along the K121—K137 section of the Zhengyao Expressway. Vegetation surveys and soil physicochemical analyses were conducted, and Pearson correlation analysis and redundancy analysis(RDA) were used to evaluate the associations between species diversity and soil variables. [Results] ① A total of 16 dominant species were recorded in the plots. The shrub layer was dominated by Amorpha fruticosa, Vitex negundo, and Broussonetia papyrifera, and the herb layer was dominated by Artemisia argyi, Setaria viridis, and Erigeron annuus.② Species diversity ranked B > D > C > A, whereas soil nutrient levels ranked C > D > A > B.③ Species diversity was significantly associated with soil factors in the 0—20 cm layer, especially total nitrogen, total phosphorus, total potassium, alkali-hydrolyzable nitrogen, and pH value. The results of redundancy analysis showed that total potassium was the main factor associated with community diversity differentiation(with an explanation rate of 15.2% and a contribution rate of 16%), and showed a significant positive relationship with species diversity. The species richness, the ShannonWiener index, and the Simpson index were significantly positively correlated with each other, whereas none of them was significantly correlated with the Pielou evenness index. [Conclusion] Soil environmental factors are the key drivers of plant community diversity differentiation on highway slopes, but higher soil nutrient levels do not necessarily correspond to higher diversity. In particular, excessively nutrient-rich conditions may constrain further increases in species diversity. During the natural restoration stage of slopes, it is recommended to focus on precise regulation of key limiting factors and overall improvement of soil health, promote the development of multispecies plant communities adapted to local conditions, and optimize community structure to construct an efficient, stable, and sustainable slope ecosystem.