To identify the coping mechanisms and the adaptive strategies of oat seedlings exposed to NaCl, NaHCO₃, and Na₂CO₃, the main salts in the soils of the salt-alkali grasslands of the Songnen Plains of China, growth rates and physiological indices of oat seedlings were measured in plants grown in soils with different concentrations (48-144 mmol/L) of the three salts. The result demonstrated that although oat seedling survival rates were unaffected by NaCl stress, the tiller number, plant height, and shoot and root dry weights decreased with increasing salt concentration, in the order of Na₂CO₃ > NaHCO₃ > NaCl. In addition, higher concentrations of Na⁺ accumulated in the shoots and roots of oat seedlings under Na₂CO₃ stress and NaHCO₃ stress than in seedlings under NaCl stress. Reductions in concentrations of K⁺ were also greater under both Na₂CO₃ stress and NaHCO₃ stress than under NaCl stress, especially in the roots. Large amounts of Cl^- and proline were found to accumulate in oat seedlings, most likely as a strategy for maintaining osmotic and ionic homeostasis under NaCl stress, whereas substantially higher accumulations of proline and organic acid were observed to balance cation deficiency under Na₂CO₃ and NaHCO₃ stresses. These results indicated that the stress effects on oat seedlings of Na₂CO₃ and NaHCO₃ exposure were greater than that of NaCl exposure, with Na₂CO₃ stress having the strongest detrimental effect. In addition, oat seedlings responded to different levels of salt stress through the adoption of various physiological mechanisms.