Abstract: Effects of different levels of NaC1 solution (CK:0g/L, S1:1g/L, $2:1.5g/L, S3:2g/L, S4:2.5g/L, S5:3g/L) on plasma membrane permeability, proline content, nitrate reductase activity of leaves and root activity of Pteroceltis tatarinovaii Maxim. seedlings were investigated under hydroponic culture conditions in a greenhouse. The results indicated that the increases in plasma membrane permeability of CK, S1 and $2 were generally lower than those of S3, S4 and $5. The increases in proline contents of CK and S1 were lower than those of S2, S3, S4 and S5, and proline contents of S3, S4 and $5 were significantly higher than those of CK, S1 and S2. Nitrate reductase activity of each treatment fluctuated as stress time progressed. Both the nitrate reductase activity of $4 and that of $5 versus stress time curves appeared the two-bell shape rather obviously; root activity of each treatment fluctuated as stress time progressed, and generally speaking, root activities of $3, $4 and $5 were highly significantly lower than that of CK. The preliminary conclusion was drawn that 2 g/L was the critical concentration of NaC1 solution which obviously affects the plasma membrane permeability, proline content and nitrate reductase activity of leaves as well as root activity of P. tatarinowii seedlings.