Syneilesis aconitifolia, with medicinal value and salt-alkali tolerance, is a potential ground cover and decorative material in gardens. To investigate the influence of arbuscular mycorrhiza (AM) fungi on the colonization and salt-alkali tolerance of S. aconitifolia, a pot experiment was conducted and the AM fungi community existing in Songnen salt-alkali grassland was selected as the inoculation. After 90 days of cultivation, NaCl and NaHCO3 solutions (50 mmol/L, 100 mmol/L, and 200 mmol/L) were applied for 10 days, subsequently, the mycorrhizal colonization, biomass, relative water content, chlorophyll content, malondialdehyde content, antioxidant enzyme activities and the level of osmotic regulation were measured. The results showed that the colonization rate and intensity decreased under saline-alkali stress, and the adaptability of AM fungi in low-concentration alkali stress was higher than that of salt stress. AM fungi could increase the biomass, relative water content, and chlorophyll content, and decrease the malondialdehyde content of S. aconitifolia to some extent. With the increase of salt or alkali solution concentration, AM fungi not only upregulated the activity of the antioxidant system, but also increased the content of osmotic regulatory substances, which indicated that AM fungi could improve the saline-alkali tolerance of S. aconitifolia. Multivariate analysis of variance (ANOVA) and radar map analysis showed that the mechanisms of resistance to salt stress and alkali stress were not the same in S. aconitifolia. In addition, the regulation of AM fungi on salt-alkali resistance of S. aconitifolia was also different. The results provided a scientific basis for the symbiosis between the local AM fungal community and S. aconitifolia, as well as data support for the restoration of saline habitat using S. aconitifolia with high medicinal value.