Global tourism intensifies ecological stress in karst destinations, hindering the conservation of World Natural Heritage sites. However, the mechanisms that underlie the effects of tourism disturbance on karst soil fungi remain unclear. This study examined Baicaoping Grassland, South China's most significant natural karst grassland tourism area. We established experimental sites representing no (ND), light (LD), moderate (MD), and severe (SD) tourism disturbance. Integrating ITS high-throughput sequencing with eight soil parameters, we systematically analysed disturbance impacts on soil chemical properties and fungal communities. Key findings: (i) The disturbance gradient significantly altered soil nutrient patterns. (ii) Ascomycota (48.01%) and Basidiomycota (28.22%) dominated at the phylum level, with unclassified_Ascomycota (17.52%) as the predominant genus. Moderate disturbance significantly increased fungal alpha diversity. Disturbance intensity strongly influenced beta diversity (p = 0.001). (iii) Tourism disturbance indirectly affected soil microbial functionality and ecological restoration capacity via alterations in fungal functional guilds. This study provides scientific references for sustainable ecological development in karst grasslands.