Abstract:The exogenous ABA in different concentrations was used to spray Zea mays L. (cv. Luyu 11) seedlings under different salinity. The growth status, osomotic potential and osmotic regulatory activity, the contents of Na+ and K+, soluble sugars and proline were determined at different time after treatment. The results were shown as follows: The exogenous ABA gave an increase in salt resistance and dry weight of corn seedlings under different salinity, this increase was as a result of inhanced osmotic adjustment activity and exclusion of sodium ions from the shoot through the action of exogenous ABA, resulting an accumulation of sodium in the roots. Moreover, the decrease of osmotic potential and the increase of osmotic regulatory activity were for reasons of enhancement of organic osmotors, instead inorganic, e.g. Na+ and K+ osmotors. The mechanism of sodium exclusion from the shoot was also discussed.