[Objective] The niche characteristics of understory herbaceous plants in Pinus tabuliformis plantation forests in the feldspathic sandstone area were explored in order to provide basic data for local Pinus tabuliformis plantations to maintain biodiversity and community stability. [Methods] The types, quantity, average plant height, and coverage of various herbaceous plants were recorded by field investigation in a well-growing P. tabulaeformis forest area. Based on the survey data, the Shannon and Levins niche breadth index, Levins niche overlap index, and ecological response were used to analyze the niche characteristics of understory herbaceous plants. [Results] ① There were 35 species of herbaceous plants in the P. tabulaeformis plantation forest in the arsenic area. Among them, Stipa bungeiensis had the largest niche breadth indexes with better performance. Because of this species’s strong adaptability, its community was in an obviously advantageous position. ② The overall niche width and niche overlap index were generally not high, and understory herbaceous species were differentiated. ③ 37.15% of understory herbaceous species were developing species, and 62.86% of species were declining species. Among the 14 dominant species, 11 were developing species. The developing species with the largest resource occupancies were S. bungeana (0.188 5), Heteropappus altaicus (0.053 1), and Cleistogenes squarrosa (0.037 9). [Conclusion] Competition among understory herbaceous plants in P. tabulaeformis plantations in the arsenic area was weak, and the community species had poor utilization of resources and environment. Most of the dominant herbaceous species were in the developing stage, indicating that the P. tabulaeformis plantation community tended to be relatively stable at this stage.