Abstract: We collected and studied 125 plant species from grasslands in the middle and western regions of Inner Mongolia, of which 104 species (83.2%), including two from the genus Carex, were infected by arbuscular mycorrhizal (AM) fungi. The colonization rate of AM fungi was higher in perennial and brush species (90.4%) than in annual and biennial plants (47.6%). Most wild plant species in the survey belonged to the Arum-type (65.38%), whereas only 19.23% belonged to the Paris-type. The intermediate type and undetermined type accounted for 10.58% and 4.81%, respectively. The results show that the structural type of AM fungi depends on the family and genus that their host plants belong to, rather than on the root forms, life forms and colonization rates of their host plants.