Abstract: In order to clarify the seed germination characteristics of alfalfa under salt stress and salt tolerance in seed germination stage, provide salt-tolerant varieties for the improvement of soil salinization and enhance the utilization rate of saline and alkaline soil, five alfalfa varieties were used as materials, the effect of different concentrations of NaCl (0, 0.4%, 0.8%, 1.2%) on the main seed germination characteristics, including germination rate, germination energy, seedling height, root length, were studied. The results showed that the main seed germination characteristics were greatly affected by salt stress. With the increase of NaCl concentration, germination rate and germination energy decreased significantly, and seedling height and root length shortened significantly. The influence of high concentration NaCl on seed germination characteristics was particularly noticeable. Different alfalfa varieties showed significant differences among different salt concentrations. Germination energy and germination rate were significantly different among different alfalfa varieties, while seedling height and root length were not significantly different among different varieties. Considering both individual index and comprehensive index of salt tolerance, under the condition of this experiment, the order of salt tolerance of alfalfa varieties was ‘Magnum salt’>‘Zhongmu No.1’>‘Victoria’ > ‘Ameristand 201T’ > ‘Phabulous’.