Abstract: Spore identification technique was employed to understand the effect of active soil organic carbon (ASOC) on the biodiversity and colonization indices of arbuscular mycorrhizal fungi (AMF). The results showed that within ASOC mass fraction ranges, Glomus had significant effect on community composition of AMF and the effect was enhanced with the increase of ASOC. Dominant species (in particular some co-occurring dominant species played an important role in community structure of AMF. ASOC mass fraction was positively correlated with spore density, and the colonization intensity and arbuscule richness were increased at the lower and intermediate ASOC mass fractions. The overall effect of AMF was great at lower ASOC level (0.81~1.40 g/kg) Our results indicate the application of AMF may have great potential in alpine steppe at lower ASOC level. This provides important information for developing suitable agricultural engineering techniques and methods to reinforce the effect of ASOC on biodiversity and infection intensity of AMF, and to increase the synergetic effects among multiple mycorrhizal species and dominant species. The result is of great significance for the sustainability of the alpine grasslands.