Objective：To investigate the preventive effect of testosterone on knee osteoarthritis in male rabbits. Methods：Eighteen male rabbits were randomly divided into castration group，noncastration group and testosterone supply group（n=6）. The rabbits in cas－tration group underwent the excision of anterior cruciate ligment and the medial meniscus on the right knee joint while those in non－castration group and testosterone supply group underwent the excision of bilateral testicles along with the treatment in castration group. Testosterone undecanoate（6 mg/kg，once every two weeks，three times in total） was injected intramuscularly to rabbits in testosterone supply group at the third week after the operation. All rabbits were killed by gas embolism at the eighth week. Macroscopic evaluation was performed on the articular cartilage of medial malleolus of femur. Insulin-like growth factors（IGF-1） immunohistochemical examination was performed in order to investigate the expression of IGF-1 in articular cartilage and the im－proved Mankin’s scores was applied to test the serum levels of total testosterone at different stages. Results：Expressions of IGF-1 were higher in noncastration group and testosterone supply group than in castration group（P<0.05）. Mankin’s scores were lower in noncastration group and testosterone supply group than in castration group（P<0.05）. The serum level of testosterone was lower in cas－tration group than in noncastration group and testosterone supply group at the fourth and eighth week（P<0.05）. Conclusion：Testos－terone has preventive effect on knee osteoarthritis in male rabbits.