This research investigates the mechanism of increased salinity tolerance of ectomycorrhizal fungi-inoculated P. sylvestris var. mongolica to provide a theo-retical basis for the application of the fungus in saline soils. Growth effects due to inoculation of seedlings with Suillus luteus (a symbiotic ectomycorrhizal fungus), were deter-mined in four kinds of saline–alkali soils. Growth and physiological indicators, including photosynthetic charac-teristics, plant height, biomass, photosynthetic pigments, catalase (CAT) and superoxide dismutase (SOD) enzyme levels, and malondialdehyde (MDA), an organic marker for oxidative stress, and soluble protein levels were deter-mined. Mycorrhizal colonization rate decreased with increasing saline–alkalinity and growth of inoculated seedlings was significantly enhanced. Biomass and chlorophyll contents also increased significantly. SOD and CAT activities were higher than in non-inoculated seed-lings. However, MDA content decreased in inoculated seedlings. Soluble protein content did not increase signif-icantly. Inoculation with a symbiotic ectomycorrhizal fungus could enhance the saline–alkali tolerance of P. sylvestris var. mongolica. Growth and physiological performance of inoculated seedlings were significantly better than that of uninoculated seedlings. The results indicate that inoculated P. sylvestris var. mongolica seed-lings may be useful in the improvement of saline–alkali lands.