In order to explore the distribution pattern and environmental driving factors of soil fauna functional groups in poplar-birch mixed forest under different altitude gradients in Guandi Mountain, this study took the poplar-birch mixed forest, a typical forest ecosystem in Guandi Mountain Forest Area, Shanxi Province, as the survey object, set up four altitude gradients (1600 m, 1800 m, 2000 m, 2200 m), and sampled soil animals in poplar-birch forest in May, July and October from 2022 to 2023. The one-way ANOVA and LSD method were used to analyze the dynamic responses of soil fauna functional groups at different altitudes, sampling seasons and soil layers. Mantel test and redundancy analysis were used to clarify the influence of environmental factors on the spatial and temporal distribution pattern of soil fauna functional groups. The results showed that a total of 24444 soil animals were obtained at different altitudes in Guandi Mountain, belonging to 127 groups of 3 phyla, 11 classes, 34 orders (suborders), including 3 mygivorous groups, 13 omnivorous species, 23 herbivorous species, 30 predatory groups, and 54 saprophagous groups, accounting for 19.66%, 4.33%, 8.95%, 10.08%, and 56.98% respectively. In terms of temporal dynamics, the total number of soil animal functional groups increased first and then decreased with the change of months, with a trend of July> May>October, and a gradual decrease of the total number of individuals with time, with a trend of May> July> October. In terms of vertical distribution, the total number of taxa and the number of individuals gradually decreased with the deepening of the soil layer, and the change trend was O layer> A layer> B layer>C layer. In addition, the number of saprophagous soil fauna groups and the number of individuals were higher than those of other functional groups. Soil temperature, humidity, soil pH, electrical conductivity, available nitrogen, available phosphorus and available potassium were the main environmental factors that determined the spatial and temporal distribution pattern of soil fauna functional communities in Guandi Mountain. The results of this study can provide a scientific reference for the monitoring and protection of soil fauna diversity in the Guandi Mountain forest area.