Soil fungi are crucial for sustaining plant abovegroung biomass and in turn, plants influence the soil fungal community composition via root exudates. However, the impact of forest tree species on soil fungi, including the composition and diversity of their functional communities, is not well understood. In this study, Picea asperata natural forest with similar ages at two altitudes (2900 m and 3200 m) in the subalpine mountains of western Sichuan were selected to analyze the changes of soil fungi and their functional fungal communities composition and diversity by collecting the rhizosphere, non-rhizosphere and bulk soil samples. The high-throughput sequencing technology and FUNGuild database comparison were used. The results show that the composition and diversity of soil fungi and their functional fungal communities were not significantly different among the three soil sampling sites, however, there were significant differences in the composition and diversity of soil fungi and their functional fungal communities between the two altitudes. For example, the dominant fungal genera at 2900 m and 3200 m were Sebacina and Russula, respectively. For the α diversity of fungal functional community, it was found that the ACE index of ectomycorrhizal (ECM) fungal community was significantly higher at 2900 m than at 3200 m altitude, while the ACE index and Shannon index of plant pathogenic fungal community show an opposite trend, and the α diversity index of soil fungi and their saprotrophic fungal communities had no significant difference at different altitudes. Network analysis revealed significant differences in the interactions between soil fungi and their core communities at the two altitudes, with the 3200m community exhibiting a notably stronger negative correlation. In addition, the key factors affecting soil fungi and their functional fungal communities were also different. The communities of soil fungi and saprotrophic fungi were mainly affected by pH, while the communities of ectomycorrhizal fungi and plant pathogenic fungi were affected by soil moisture content and total nitrogen, respectively. This study is helpful for further understanding the microbial mechanism of forest ecosystem and providing scientific basis for forest protection and restoration.