Abstract: To better understand the relationship between the distribution of understory plants and environmental factors in Pinus tabuliformis plantation, the occurrence and distribution of understory plants were investigated on 42 plots in Songjiagou of Taiyue Mountain, Shanxi Province, China. The environmental factors controlling understory plant composition and diversity were quantitatively assessed by the method of canonical correspondence analysis (CCA). The results showed that: 1) 83 understory species belonging to 26 families and 72 genera were recorded on 42 plots. The number of species in the herb layer was more than 3 times of that in the shrub layer. 2) The results of CCA clearly reflected the relationship between the distribution of understory plants and environmental gradients. Forward variable selection showed that stand age, slope, slope aspect, canopy cover, total nitrogen and total potassium were important factors determining plant distribution in the herb layer, while stand age, slope aspect, slope, and total nitrogen were important in the shrub layer. 3) Habitat and biotic factors together explained 40.3% and 42.9% of variance in the distribution of herbaceous and shrub plants, respectively. Pure habitat factors exhibited a strong interpretation power for understory species distribution, suggesting that habitat factors might play an important role in the distribution variation of understory plants. The results of the study would provide a reference for scientific management, biological protection and sustainable utilization of P. tabuliformis plantation.