Abstract: In order to study the tolerance of different alfalfa varieties under sodium sulfate alkali stress and screen for alfalfa varieties with strong resistance,four alfalfa varieties were used as experimental materials.The effect of different concentrations of sodium sulfate(50,100,150,200,250 mmol·L^-1) on salt-alkali tolerance of different alfalfa varieties’ seeds were studied.And the membership function method to comprehensively evaluate the salt-alkali tolerance of seeds during the germination period was used.The results showed that different alfalfa varieties exhibited different trends in seed germination indicators（germination rate,germination potential,germination index,vitality index） and seedling growth indicators（embryonic root length,embryonic axis length,fresh weight per plant,and dry weight per plant） under different concentrations of sodium sulfate stress.A salt-alkali concentration of 100 mmol·L^-1 can effectively reflected the differences in salt-alkali tolerance among alfalfa varieties.The WL343HQ alfalfa seeds had the highest salt-alkali tolerance coefficients for germination rate,germination potential,germination index,and vitality index,with values of 44.08,20.00,20.73 and20.55,respectively.The WL343HQ alfalfa sprouts had the highest salt-alkali tolerance coefficients for embryonic root length,embryonic axis length,and fresh and dry weight per plant of Longmu 806 alfalfa sprouts,with values of 49.93,29.38,48.55 and 69.23,respectively.According to the analysis of the membership function values and comprehensive evaluation D-values of the salt alkali tolerance coefficients of various indicators during the seed germination period,the salt-alkaline tolerance of the four alfalfa varieties was as follows:WL343HQ＞WL525HQ＞ Longmu 806＞ Longmu 807.The four selected alfalfa varieties had significant differences in resistance to sodium sulfate salt alkali,WL343HQ had the strongest sal-alkali resistance.