Alfalfa （Medicago sativa）seedlings was conducted with 16 different salt-alkaline conditions (salinity 25-150 mmol·L^-1 and pH 8.39-10.90) by mixing four salts (NaCl,Na₂SO₄,NaHCO₃ and Na₂CO₃) in various proportions．We studied survival rate,plant height,total biomass,soluble protein content,proline content,ferulic acid and salicylic acid of alfalfa seedlings with Glomus mosseae under mixed salt-alkaline stresses by indoor pot experiment．Results showed that:(1)plant height,total biomass,soluble protein,proline content of inoculated plants were increased by 20%,130%,9.6%,3% respectively than non-inoculated plants under non- salt-alkaline stress conditions.While ferulic acid and salicylic acid were decreased by 59.1%,623.9% respectively than non-inoculated plants in natural conditions.(2) Under salt-alkaline stress conditions,whether or not inoculation of AMF（arbuscular mycorrhizal fungi）,the survival rate,plant height,biomass and soluble protein of alfalfa were decreased with the increase of salt-alkaline degrees.However the proline content,ferulic acid and salicylic acid content of alfalfa were increased.The survival rate,plant height,total biomass,soluble protein and proline of inoculated plant were better than non-inoculated plants with significantly different.Salicylic acid content of inoculated plant was lower than that of non-inoculated plants with significantly different and higher levels of ferulic acid but the difference was not significant.In conclusion,under mixed salt-alkaline conditions,inoculated AMF can change the content of phenolic acids,accumulate osmotic regulation substances,promote the growth and improve saline-alkaline tolerance of alfalfa.It is important for improving economic crops in the salt-alkaline soil and promoting AMF play a role in production.