Abstract: The activities of polyphenol oxidase (PPO), peroxidase (POD) and superoxide dismutase (SOD) in the different tested cotton plants inoculated with Fusarium moniliforme, the causal organism of cotton red rot, were tested and analyzed respectively by applying artificial inoculation in greenhouse to explore the relationship between the enzyme activities and the resistance of cotton plants to the disease and to provide the evidences for the breeding of the disease-resistant cotton varieties. The results indicated that after being inoculated with Fusarium moniliforme, the activities of the three enzymes in the tested cotton plants all rose obviously, and that the enzyme activities in the disease-resistant Zhongmian-29 were higher than those in the disease-sensitive Simian-3. Meanwhile, the enzyme activities in Zhongmian-29 rose more rapidly than in the disease-sensitive Simian-3. It was suggested that the activities of PPO, POD and SOD in cotton plants were closely related to the resistance of cotton plants to the disease. The three enzymes played an important role in the resistance of cotton plants to the disease. The results would be valuable to the identification of disease-resistance of cotton varieties and to the breeding of the disease-resistant cotton varieties.