The diversity of arbuscular mycorrhizal fungi (AM) was investigated in cultivated and natural fold sites or chungbuk, Korea. soils were collected from rhizosphere or Sorghum bicolor, Fagopyrum esculentum and Glycine max in cultivated sites, and of Miscanthus sinensis, Glycine soja and Lespedeza cuneata in natural sites. Total 20 species of Glomalean fungi were found in this study. Species richness, species diversity and density of AM fungi were significantly lower in the arable sites. While only AM fungal spores belong to Glomus and Acaulospora were found in arable fold sites, more diverse fungal spores including Gigasporaceae were found in natural grasslands. AM fungal spore composition did not significantly differ among crop plant species. Results suggest that the agricultural practices were significantly influenced on AM fungal community structures and mycorrhizal developments.