To study the antioxidant activity of Cordyceps sinensis, Cordyceps militaris and Cordyceps Kyushuensis, and to observe the effect of experiment condition on the results. The chemiluminescence was used to determine the activity of three Cordyceps sp. On scavenging superoxide anion radicals (O 2-). Results: In three Cordyceps sp., Cordyceps militaris had the highest antioxidant activity; Cordyceps sinensis and Cordyceps kyushuenis had near antioxidant activity. It is showed that Cordyceps militaris and Cordyceps kyushuenis have good prospects, and also can be hoped to be applied in clinic by replacing Cordyceps sinensis.