Abstract: To provide a theoretical basis for the scientific development of alfalfa industry in arid area, three alfalfa varieties, ‘Longdong’, ‘Daye’ and ‘Argangjin’ were used as test materials. Biomass, root-crown ratio, the percentage of dry matter accumulation, net photosynthetic rate, transpiration rate, water use efficiency, stomatal conductance, and the content of chlorophyll a, chlorophyll b and carotenoid were tested under different drought stresses by pot-cultivation experiment. The results showed that with the decrease of relative soil water content, net photosynthetic rate of three alfalfa varieties decreased slowly, ‘Argangjin’ could maintain a relatively higher net photosynthetic rate than ‘Longdong’ and ‘Daye’, and expressed better potential photosynthetic capacity. The total biomass of the three alfalfa varieties reduced, the decrease extent of ‘Daye’ was the lowest, and it still maintained relatively higher total biomass. Root-crown ratio and the percentage of dry matter accumulation of ‘Longdong’ and ‘Argangjin’ increased with the decrease of relative soil water content, and were extremely and significantly higher than that of ‘Daye’. Along with the increasing degree of drought stress, the content of chlorophyll a, chlorophyll b and carotenoid and the Chla/Chlb value of ‘Daye’ increased. In conclusion, ‘Daye’ has the highest biomass, while ‘Argangjin’ has the strongest drought resistance.