Two contrasting rice (Oryza sativa L.) cultivars, i.e.Wuyujing No.3 (salt-tolerant) and IR36 (salt-sensitive), were used for investigating effects of exogenous calcium (Ca) on antioxidant enzyme activity and lipid peroxidation in leaves of rice growing hydroponically under salt stress.The results show that content of malondialdehyde (MDA) as well as membrane permeability were enhanced under salt stress.Salt stress decreased activities of antioxidant enzymes and contents of antioxidants.Addition of Ca significantly enhanced activities of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD) and ascorbate peroxidase (APX) in the leaves of salt stressed rice but reduced concentration of MDA and permeability of cell membrane.Furthermore, exogenous Ca enhanced ascorbic acid (AsA) content and root activity.Treatment with higher Ca (10 mmol L^-1 Ca²⁺) was observed to have better alleviat ing effect than that with lower Ca (5 mmol L^-1 Ca²⁺) in the two contrasting rice cultivars differing in salt tolerance, but the reverse was observed in the experiment of APX activity.The degree of increase or decrease in the above mentioned parameters was smaller in salt tolerant cultivar than in salt sensitive one under single NaCl stress.The results seem to suggest that the elimination of active oxygen species (AOS) and maintenance of membrane stability accounted to some extent for the mechanisms of Ca-mediated enhancement of salt tolerance in rice growing under salt stress.