In order to alleviate freshwater shortage in salinization area, use the saline water more scientifically and rationality, and improve the yield of alfalfa, taking Zhongmu No.1 as the materials and freshwater (mineralization degree of 1 g/L) as contrast, the experiments were conducted to learn the effect of saline water (mineralization degree of 3 g/L, 5 g/L and 7 g/L) on germination percentage and plant height of alfalfa. The results showed that the germination percentage and plant height had no significant difference between 3 g/L and fresh water, but it showed great difference when the mineralization degree raised to 5 g/L and 7g/L. The results indicated that, in order to ensure the germination percentage more than 80%, the mineralization degree should be controlled to less than 4.48 g/L. When the satisfied plant height was attained, the mineralization degree should less than 4.66 g/L, otherwise, the growth of alfalfa would be inhabited by long-term salt stress.