This study was designed to explore the functions of soil fungal communities in the Cd tolerance of Q. acutissima seedling. Three Cd levels of 15, 30, and 40 mg kg−1 were set up using the soils collected from Q. acutissima forests. The benomyl was applied to inhibit the fungal communities in the soil. Following a 100-day pot cultivation of Q. acutissima seedlings, the plant growth, Cd content, N uptake, and fungal communities were evaluated. The results showed that the root dry weights were significantly reduced after the benomyl addition at the Cd concentrations of 30 and 40 mg kg−1. Root fungi colonization was enhanced under higher Cd concentrations when soil fungi are present (without the benomyl treatment). The fungi associated with root increased the Cd accumulation in the roots while decreased the Cd transfer to the shoot at 40 mg Cd kg−1. The 15N enrichment in root tip was positively correlated with enzyme activities of soil catalase and urease. And the activities of acid phosphatase, catalase, and urease were inhibited at each Cd level. The abundance of the dominant fungal genus differed in their response to Cd contamination. The ectomycorrhizal fungi of Tomentella and Cortinarius were identified under the higher Cd levels (40 mg kg−1). Our results implied Tomentella and Cortinarius could be applied to enhance the capacity of Quercus acutissima in the bioremediation of Cd polluted soil.