In order to explore the possible physiological mechanisms of ameliorating nickel toxicity by calcium,this paper used pot culture to study the amelioration of nickel toxicity on soybean seeding by external calcium and its effect on the activity of SOD,CAT,POD,APX in leaf tissue.The results showed that the growth of soybean seeding was inhibited significantly when added Ni2+ was more than 60 mg/kg.But the nickel toxicity symptom was ameliorated to different degrees as adding different amount of calcium,and the treatment of 200 mg/kg Ca2+ was better than 100 mg/kg Ca2+.Compared with no nickel added,the activities of SOD,CAT and APX in leaf tissue decreased significantly in the treatment of 60 mg/kg Ni2+,but POD increased obviously.When Ca2+ was combined,the activity of SOD,CAT,POD,APX in leaf tissue was improved obviously and the treatment of 200 mg/kg Ca2+ increased greater than 100 mg/kg Ca2+.It was suggested that Ca2+ameliorated the nickel toxicity symptom through improving the activities of antioxidase in leaf tissue and enhancing the scavenging activity of active oxygen.It was one of mechanisms of external calcium ameliorating nickel toxicity on soybean seedlings.