Pinus tabuliformis is a dominant tree for soil conservation and water conservation in the arsenic sandstone region of the Loess Plateau, one of the most serious areas of soil erosion in China. The Levins ecotone width index, Pianka ecotone overlap index, and redundancy analysis (RDA) were applied to study the ecotone characteristics of understorey herbaceous communities and their interactions with the environment in several different stand types of planted P. tabuliformis forests.On the basis of the variation among sites,the planted forests of P. tabuliformis were classified into six types.At each site,topography ( slope,aspect,and slope position) and forest stand characteristics(canopy density,stand density) of P. tabuliformis was recorded,herb species were measured in 1×1m² quadrats,and soil samples were collected adjacent to each quadrat.In this study,we used the niche breadth and Niche overlap indices for analysis of herb species ecological niche characteristics under different site types of P. tabuliformis forests in a feldspathic sandstone region,and studied the relationship between ecological niche characteristics and the environment through CCA and RDA.The results showed that 31 species of herbaceous plants belonging to 11 families and 24 genera were found in the 150 herbaceous samples of P. tabuliformis sylvestris understorey surveyed, with a predominance of positive dry plants. The ecological niche characteristics of the herbaceous communities in different types of P. tabuliformis forests were different. The ecological niche width index and the ecological niche overlap index both showed that the sunny slopes were larger than the shady slopes, and the flat slopes were better than the gentle slopes, but the overall indices were smaller, indicating that the species used the environmental resources to a less extent, the interspecific competition was not too great, and the communities were in a relatively stable state. By comparing canonical correspondence analysis (CCA) and redundancy analysis (RDA), the RDA ranking better reveals the relationship between ecological niche characteristics and environmental factors. It concludes that tree and shrub layer depression, soil organic matter, soil water content and slope were the dominant environmental factors for the different ecological niche characteristics of understorey herbaceous communities.