Rudbeckia hirta not only had the ability of cold，drought and saline-alkali resistance, but also was the most commonly used ground cover plant in urban landscaping. In this study, Funneliformis mosseae was selected as the inoculant substrate in pot experiments. 70 days after the colonization, NaCl and NaHCO₃ solutions at different concentrations (0, 65, 135, 195 and 260 mmol·L^-1) were subjected to salt or alkali stress. After 10 days of treatment, we determined AM fungal colonization, chlorophyll content, malondialdehyde (MDA) content, antioxidant enzymatic activity and osmotic regulation substance, so as to clarify the effects of AM fungus on the root colonization status and salinity tolerance of R. hirta and to provide a theoretical basis for the use of R. hirta to repair saline-alkali soil and the application of AM fungi in practical production. The results showed that: (1) compared to control, colonization rate and colonization intensity of AM fungi under salt stress were significantly reduced, while the trend of rising and then decreasing under alkali stress was shown. (2) Under saline-alkali stress, AM fungi could increase chlorophyll content and decrease MDA content in leaves of R. hirta to a certain extent compared with uncolonized plants. As the concentration of saline-alkali solution increases, AM fungi could not only improve the R. hirta proline, soluble sugar and soluble protein contents of osmotic regulation substances, also could enhance plant activities of superoxide dismutase (SOD), peroxidase (POD) and ascorbate peroxidase (APX), which indicated that inoculation of AM fungi could improve the saline-alkali tolerance of R. hirta. (3) PCA analysis showed that the resistance mechanisms between salt stress and alkali stress were not the same，with chlorophyll, MDA, POD, SOD, proline and soluble sugar as the main factors in salt stress, and SOD, CAT and proline as the dominant factors in alkali stress. In addition, VPA analysis also showed that AM fungi had a greater effect on the overall physiological characteristics of R. hirta than saline-alkali stress. The results showed that low alkali stress could promote the colonization of R. hirta by AM fungi, and inoculation of AM fungi could significantly reduce the MDA content of R. hirta under saline-alkali stress, improved antioxidant enzyme activity and osmoregulatory substance accumulation, so as to improve the salinity tolerance of R. hirta.