Due to climate change, agriculture, animal husbandry production, and ecological environments have been seriously influenced by global soil salinization. Salt stress generally has been the focus of numerous studies, resulting in alkaline stress being ignored, when, in fact, salinization frequently occurs with soil alkalization. Actually, high pH levels co-exist with salinity in alkaline soil. The present study attempts to investigate the effects of inoculation with arbuscular mycorrhizal fungi (AMF) and rhizobia on the growth of alfalfa (Medicago sativa L.) under saline-alkaline stress (SAS). Based on the characteristics of Chinese saline-alkaline soil and a mixed orthogonal design L₁₆(16¹×2²), of an indoor pot experiment, alfalfa seedlings were inoculated with AMF (Funneliformis mosseae), rhizobia, both, or neither under 16 different saline-alkaline conditions (salinity 25-150 mmol/L and pH 7.67-10.52). The conditions were created by mixing four types of salts (i.e., NaCl, Na₂SO₄, Na₂CO₃, NaHCO₃) in various proportions. The effects of inoculation with AMF and/or rhizobia on the growth of alfalfa under mixed SAS were studied. The results showed that shoot length was influenced by factors in the order of AMF+rhizobia > pH > AMF > SAS > rhizobia. The factors that affected shoot biomass, root biomass, high net growth of stem, malondialdehyde (MDA) and proline were ordered most to least as pH > SAS > AMF+rhizobia > AMF > rhizobia, and they affected SOD, POD, and protein ordered most to least as pH > AMF+rhizobia > SAS > AMF > rhizobia, pH > AMF+rhizobia > rhizobia > AMF > SAS, and pH > SAS > rhizobia > AMF+rhizobia=AMF, respectively. The shoot length, root biomass, and POD of seedlings inoculated with rhizobia and AMF showed the maximum responses. The root nodule numbers and weight of alfalfa inoculated with AMF and rhizobia were slightly more than that of alfalfa inoculated with rhizobia alone, but the differences were not significant. The results suggested that SAS would strongly inhibit the growth and development of alfalfa and the damage was greater than that caused by salt stress or alkaline stress. However, inoculating rhizobia or AMF could significantly improve the salt tolerance of alfalfa (salinity ≤ 75 mmol/L, pH 7.0-9.79) and alleviate the inhibition of alfalfa's growth under saline-alkaline stress. In terms of the different methods of inoculation, the dual inoculation of rhizobia and AMF worked best, the effect of inoculating with only rhizobia was second, and inoculating with rhizobia showed the lowest effect in the alleviating process. However, the positive effects of AMF and/or rhizobia cannot completely offset the negative impact of SAS (salinity:100-150 mmol/L, pH 9.87-10.52). This result could provide some reference for reducing damage of SAS on alfalfa, improving resistance of seedlings to SAS, and utilizing saline-alkaline soil. It can also be applied to agricultural production practices.