Abstract: The s eedlings of Puccinellia tenuiflora were domesticated by sodium carbonate progressively, the results indicated that increasing alkalinity stress intensity progressively could relax the inhibition of Na₂CO₃ upon the increasing of fresh and dry weight of seedlings and the injury of which upon cell membrane of seedlings to some extent, thus could increase the resistance of seedlings to the stress of Na₂CO₃.And the limit of alkaline resistance of Puccinellia tenuiflora seedlings was discussed.