The oat variety ‘Baiyan No.2’ was used as the material. Setting the salt solution (NaCl∶Na₂SO₄=5∶1) and the alkali solution (NaHCO₃∶Na₂CO₃=5∶1) with 0, 50, 100, 150, 200 mmol/L, respectively, we carried out the potting experiments in the greenhouse. The growth rate, plant water content, leaf ion content and leaf organic acid content of oat were detected. We analyzed the effects of the salt stress and alkali stress on oat ion balance and compared the adaptability of oat to the two types of stress. The results showed that: (1) the plant growth rate and plant water content increased under lower salt stress (50 and 100 mmol/L), and decreased under higher salt stress (150 and 200 mmol/L). However, it depressed with the alkali stress concentration increasing. At the same saline concentration, the influence of alkali stress on plant is greater than salt stress. (2) The contents of K⁺, Ca²⁺, Mg²⁺, SO^2-₄, H₃PO^-₄ and NO^-₃ decreased with the concentration increasing of both salt stress and alkali stress. The contents of Na⁺, Cl^- and SO^2-₄ increased significantly under salt and alkali stress. For example, comparing with CK, at the 200 mmol/L of salt stress and alkali stress, Na⁺ increased 367.15% and 518.41%, respectively; Cl^- increased 785.07% and 52.59%, respectively; SO^2-₄ increased 142.01% and 52.86%, respectively. (3) At 200 mmol/L of the salt stress and alkali stress, the organic acids increased 74.52% and 1 232.34%, respectively. The contents of citrate, aconite, succinate and malic acid were higher in oat leaves under alkali stress and higher concentration of salt stress, and the aconic acid is the main component of total organic acids under both salt stress and alkali stress, citric acid and succinate acid were changed significantly, there were less formic acid, acetic acid, lactic acid, malate acid and oxalic acid. It is concluded that the effect of the alkali stress is more harmful on oat plant growth rate, plant water content, leaf ion content and organic acids than salt stress. Both salt stress and alkali stress caused the accumulation of cation (Na⁺) in oat leaves. Futher, it blocked the absorption of K⁺, Ca²⁺, Mg²⁺, H₃PO^-₄, and NO^-₃. The oat leaves accumulate Cl^- to adjust the leaf ion balance under salt stress, while, it accumulate organic acids under alkali stress to adjust the ion balance. Organic acid is the specific metabolites in response to alkali stress, and aconic acid is the main component of organic acids.