Trifolium repens was used as material to study the effect of salt stress on SOD,POD,MDA,CAT of the stem.The results showed that: SOD activity and POD activity increased firstly,then decreased with the increase of NaCl concentrations and the prolonging stress time.CAT activity increased at first and then decreased when salt stress vary from 50 to 250 mmol·L^-1.Antioxidant enzyme activity decreased,mem-brane seriously harmed,MDA content increased and reached a maximum under 200 mmol·L^-1 NaCl,and then decreased gradually with the increase of NaCl concentrations and the prolonging stress time.