Pot experiment was conducted to set up gradient salinealkali environment (0, 1.5, 3.0, 4.5, 6.0 and 7.5 g·kg^-1) and inoculate Rhizophagus intraradices (Ri). The changes of seedling height growth, leaf photosynthesis, chlorophyll fluorescence parameters and stress resistance physiological indexes of Pyrus betulifolia seedlings were compared and analyzed. We studied the effects of arbuscular mycorrhizal fungi inoculated with mixed salinealkali on the growth and stress resistance of P. betulifolia seedlings to provide a theoretical basis for mycorrhizal P. betulifolia afforestation in salinealkali environment. The results show that: (1) R. intraradices could form a good symbiosis with the root system of P. betulifolia, but the infection rate decreased to 47.98% and 32.97% at 6.0 g·kg^-1and 7.5 g·kg^-1 saline alkali concentration, respectively. (2) Under salinealkali stress, Ri inoculation significantly increased height growth and biomass, photosynthetic pigment content and net photosynthetic rate of P. betulifolia leaves. Especially at high saline alkali concentration (6.0 g·kg^-1and 7.5 g·kg^-1), RI inoculation significantly increased the stomatal conductance and intercellular carbon dioxide content of P. betulifolia leaves, which was conducive to the increase of photochemical quenching coefficient and the decrease of non photochemical quenching coefficient, and promoted the improvement of actual photochemical efficiency. (3) Ri inoculation significantly decreased the cell membrane permeability and the content of MDA, significantly increased the activities of superoxide dismutase and peroxidase, and increased the contents of soluble sugar and soluble protein in the leaves of P. betulifolia seedlings. It was found that inoculation with R. intraradices could significantly enhance the activities of antioxidant enzymes and osmotic mediation ability of P. betulifolia under salinealkali stress, effectively enhance its growth and photosynthetic efficiency, and finally alleviate the damage caused by saline alkali stress. Therefore, the implementation of mycorrhizalization of P. betulifolia seedlings can effectively improve the growth and stress resistance of seedlings in salinealkali soil, which is beneficial to play a greater role in the comprehensive management of salinealkali soil.