[Objective] To explore the differences in the relationship between herbaceous diversity and soil physicochemical properties of different stand types, [Methods] Four typical plantations in the loess region of northwestern Shanxi Province, including Pinus tabuliformis pure plantation, Populus microphylla pure plantation, P. tabuliformis and P. microphylla mixed plantation, and P. microphylla and Caragana korshinskii mixed plantation, were studied to analyze the differences in herbaceous diversity and soil physicochemical properties among different stand types, and to study their correlations. [Results] 1) There were 35 species of understory herbs in 12 families and 30 genera in the study area, and the dominant species were Poaceae. There were significant differences in the Simpson diversity index, Pielou evenness index, and Margalef richness index among the four typical plantations（p＜0.05）, with the P. microphylla and C. korshinskii mixed plantation showing the highest values. 2) There were also significant differences in soil physicochemical properties among the four typical plantations（p＜0.05）, with the P. microphylla pure plantation and the P. microphylla and C. korshinskii mixed plantation exhibiting the best soil properties. 3) Correlation analysis and redundancy analysis showed that there were differences in the effects of soil total phosphorus and soil water content on herbaceous diversity among different stand types. Soil water content was negatively correlated with herbaceous diversity in P. tabuliformis pure plantation（p＜0.05）, but positively correlated with herbaceous diversity in mixed forest（p＜0.05）. Soil total phosphorus was significantly positively correlated with herbaceous diversity in P. tabuliformis pure plantation, and in P. microphylla and C. korshinskii mixed plantation（p＜0.05）, and negatively correlated with herbaceous diversity in P. microphylla pure plantation, and in P. tabuliformis and P. microphylla mixed plantation. [Conclusion] Soil total phosphorus and soil water content are the main factors affecting herbaceous diversity. The results of this study are of great significance for understanding the ecological functions of understory herbaceous plants and soil properties in the loess region of northwestern Shanxi Province.