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Cabbage seedlings were grown hydroponically to study the effects of different concentrations of seawater on the seedling growth, ion content under one-fourth strength Hoagland's nutrient solution in the greenhouse. The biomass of various organs of cabbage seedlings as well as the whole plants was significantly higher in the treatments with 1 g and 2 g sea salt/L than the no-salt control, but the treatments with 4, 5 or 6 g sea salt/L caused a decrease in growth. Root/shoot ratio remained at the level of control regardless of the sea salt treatment. Na+ and Cl- concentration in different parts of cabbage seedlings increased significantly, whereas K+ and Ca2+ concentration generally increased at low concentrations of sea salt and then decreased with increasing seawater concentration. Sodium and K+ concentrations were significantly higher in the stems than roots and leaves regardless of the sea salt treatment. The sea salt treatment increased Mg2+ concentration in stems and leaves of cabbage seedlings. An increase in Na+ and Cl- concentration in roots, stems and leaves of cabbage seedlings was the main contributor to declining ratios of K+/Na+, Ca2+/Na+ and Mg2+/Na+. The obtained data suggest that cabbage seedlings have strong ability to sustain seawater stress by the regulation of transport and distribution of ions.