Abstract: In the present paper the effects of Sal, an active component isolated from Kadsura Longipenduculata Finet et Gagnep, on oxygen free radical induced injury of murine spleen lymphocytes in vitro and in vivo were investigated. The results showed that Sal at 1×10^-4 mol·L^-1 significantly inhibited the decrease of GSH content induced by Fe²⁺-Vit C and the increase of MDA formation induced by Fe²⁺-Cys in murine spleen lymphocytes. The decrease of membrane fluidity of lymphocytes under lipid peroxidation induced by Fe²⁺-Vit C was prevented by Sal. The damage of the lymphocyte surfaces induced by Fe²⁺-Vit C was also markedly reduced by Sal. Administration of Sal 20 mg·kg^-1·d ^-1 for 8 d significantly increased the GSH content of the spleen lymphocytes in mice under high oxygen stress. Meanwhile, the compensative increase of SOD activity in the spleen lymphocytes was reversed. The results suggest that Sal may protect murine spleen lymphocytes from the injury induced by oxygen free radicals.