Abstract: Background Pinus sylvestris var. mongolica is one of the most commonly used tree species for large-scale greening in northern China, and in-depth investigation of the structural and functional characteristics of root-associated fungal communities in P. sylvestris, along with their soil driving factors is crucial for understanding its growth adaptation mechanisms and ensuring forest sustainability management. Methods This study takes the P. sylvestris plantation located in the Saihanba Mechanical Forest Farm, Chengde City, Hebei Province. Using high-throughput sequencing technology, the study analyzes the structure and functional characteristics of root-associated fungal communities in young (18 years), middle aged (26 years), near mature (37 years) and mature (50 years) P. sylvestris plantations, and also explores the influence of soil properties on root-associated fungal communities. Results 1) Root-associated fungal diversity in P. sylvestris plantations exhibited significant differences with increasing forest age, and the change trend was first decreasing, then increasing and then decreasing again. there was no significant correlation between soil properties and root-associated fungal diversity. 2) Root-associated fungi in P. sylvestris plantations within the study area were classified into 9 phyla, 32 classes, 76 orders, 148 families, and 243 genera， Ascomycota（72.25%） and Basidiomycota（25.8%） occupy the absolute phylum level. The dominant genus in the young forest is Leptodophora, while the dominant genus in other stages is Phialocephala. 3) Soil properties contribute more than forest age and location to the root-associated fungal community of P. sylvestris. Among these soil properties, soil total carbon is the most important soil factor in shaping the structure of the root-associated fungal community. 4) The main trophic mode of root-associated fungal in the young stage is saprotrophyic, while at other stages, symbiotic is the main type, and endophytic fungi occupy a dominant position in the ecological functional groups. Soil total carbon and organic carbon are significantly negatively correlated with the relative abundance of symbiotic fungi. Conclusions The root-associated fungal community of P. sylvestris in the Saihanba region exhibits complex and diverse species composition, with significant differences in diversity observed across different forest ages. Soil total carbon is the most important soil factor in shaping the structure of root-associated fungal communities. The dominant trophic mode are saprotrophic and symbiotic fungi.