Abstract: OBJECTIVE To study the effects of Lycium ruthenicum Murr. aqueous extract on oxidative stress induced by exercise fatigue. METHODS One hundred and fifty mice were randomly divided into 3 groups, 50 in each group:no swimming group, immediate after swimming group and restore 30 min after swimming group. Mice in each group were subdivided into 5 groups of 10 each:positive control group, blank control group and Lycium ruthenicum Murr. low, medium and high dose group. After 30 d of intragastric administration, the contents of MDA, LPO and ROS, and the activities of SOD, CAT, GSH-Px in serum were measured. At the same time, the in vitro free radical generation system was used to evaluate the scavenging power of Lycium ruthenicum Murr. on 1,1-diphenyl-2-trinitrophenylhydrazine (DPPH),·OH and O₂^-·. RESULTS Lycium ruthenicum Murr. could not only reduce the contents of MDA, LPO and ROS in the serum of mice after swimming and 30 min after swimming significantly, but also increase the activities of SOD, CAT and GSH-Px. Moreover, it could reduce the production of DPPH,·OH and O₂^-·radicals. CONCLUSION Lycium ruthenicum Murr. can alleviate the oxidative stress caused by exercise fatigue obviously.