The influence of the arbuscular mycorrhizal (AM) fungus, Glomus mosseae, on characteristics of growth, membrane lipid peroxidation and soluble sugar content in the shoots and roots of soybean (Glycine max) plants was studied in pot culture under salt stress. The experiment was arranged as a factorial in Randomized Complete Block Design (RCBD) with four replications in greenhouse of College of Agriculture, Tehran University, Iran. The plants inoculated with mycorrhiza had significantly greater shoot and root biomass than the nonmycorrhizal plants at all salinity levels. AM symbiosis decreased membrane relative permeability and malondialdehyde content in shoots and roots. The soluble sugar content in roots was higher in mycorrhizal than nonmycorrhizal plants, but there was no significant difference in soluble sugar content in shoots between mycorrhizal and nonmycorrhizal plants. The results indicate that the AM fungus is capable of alleviating the damage caused by salt stress on soybean plants by reducing membrane lipid peroxidation and increasing the accumulation of soluble sugar content. Consequently, arbuscular mycorrhiza formation highly enhanced the salinity tolerance of soybean plant, which increased host biomass and promoted plant growth.