Abstract:Hydroponics experiments were conducted to study the changes of biological aspects under different levels of NaCl and compound-salt stress with the seedlings of Ammopiptanthus mongolicus. The effect of varying concentrations of Phosphate fertilizer solutions on the tolerance under salt stress was also evaluated. The result indicated that, the tolerance under the NaCl stress was stronger than that under compound-salt stress. When the concentration was below 0.7%, the growth was normal, when the concentration surpassed 0.8%, the mortality rate increased, and under the concentration of 1.0% the mortality rate was 86%. The tolerance under the compound salt stress was weak. When the concentration was 0.6%, the mortality rate achieved 93.3%. Proper phosphate fertilizer enhanced the seedling tolerance under NaCl stress as well as made sprout stronger.