Abstract: Using ‘Kagemusya’ (Lycopersicon esculentum Mill.) as rootstock and ‘Baoda 903’ as scion, grafting was made to compare the differences in plant growth, activities of antioxidant enzymes, metabolism of reactive oxygen species and contents of osmotic adjustment substances in leaves between grafted and own-root tomato seedlings grown hydroponically under 80 mmol/L Ca(NO3)2 stress. The results showed that Ca(NO3)2 stress significantly reduced plant growth, but significantly increased the activities of antioxidant enzymes, increased O2.- producing rate and contents of hydrogen peroxide (H2O2), malondiadehyde (MDA), proline and soluble protein in both grafted and own-root seedlings. The biomass production of grafted seedlings, activities of antioxidant enzymes and contents of proline and soluble protein in leaves of grafted seedlings were significantly higher than those of own-root seedlings, while O2.- production rate, contents of H2O2 and MDA in leaves of grafted seedlings were significantly lower than those of own-root seedlings under Ca(NO3)2 stress. These results indicated that higher activities of antioxidant enzymes, high contents of osmotic adjustment substances and less oxidative damage might be involved in the stronger salt tolerance of grafted tomato seedlings.