Abstract: To study the effects of microorganism agent on saline soil and choose salt tolerant alfalfa cultivars, the effects of microorganism agent on soil desalination rate and alfalfa growth were studied by conducting a pot experiment under different salt stress levels, and the interaction between microorganism agent, alfalfa varieties and salt stress degree were also discussed. The results showed that the microorganism agent had a significant effect on increasing the soil desalination rate, and the soil desalination rate in 020cm soil layer under applying microorganism agent treatment was increased by 9.04% compared to that of no microorganism agent treatment. Salt stress significantly affected alfalfa biomass, which represented that alfalfa biomass was decreased with the increase of salt stress degree. The three alfalfa cultivars had significant differences in salt tolerance, and the sequence from high to low was Laobo, Baoding and Sandeli. Consequently microorganism agents and salt tolerant alfalfa cultivars have good effects on soil salinity control and growth of alfalfa.