An experiment was carried out in the greenhouse using a three-compartment rhizobox system to study effects of inoculation of arbuscular mycorrhizal fungi Glomus etunicatum,Glomus intraradices and Glomus mosseae on Festuca rubra and Agrostis hugoniana,and soil environment.Results indicate that inoculation had significant effects on AM fungi infection of the plants and plant growth,increasing dry matter and P contents of both ground parts and roots and phosphorus absorption rate of the plants,improving microbial flora in the rhizaphere and water stability of soil aggregates.The mycorrhizal effects was better on Agrostis hugoniana plants than on Festuca rubra,and Treatment Festuca rubra+Glomus mossene and Agrostis hugoniana+ Glomus intraradices were better than the others in each group.The root chamber more microorganisms of various kinds than the other two,but the mycorrhizal chamber had a higher ratio of actinomycetes,especially of bacteria and fungi,which meant the difference between rhizosphere and mycorrhizosphere became small.All treatments on inoculation rate and hyphal density accorded with each other.The higher the inoculation rate,the higher the hyphal desity.Mycorrhizal hyphal contribution to the formation of water-stable soil aggregates of 5～2 mm was 100% within the distance of 4～6 cm from the root surface,however not within the distance of 0～2 or 2～4 cm.The hyphai also had significant effect on water-stable soil aggregates(more than 70%) within the distance of 2～1 mm,but significantly less than within distance of 0～2 and 4～6 cm,and did not show the rising effect with the hyphal density.Effect of Arbuscular mycorrhiza on steppe plants and infection rate of steppe plants varied with species of the mycorrhiza and plants.The effect on Agrostis hugoniana was greater than on Festuca rubra in all inoculation treatments,and the effect of the combinations of Festuca rubra+Glomus mosseae and Agrostis hugoniana+Glomus intraradices were more significant than others.