The polypeptides (PCF) were isolated from Chlamys farreri (Mr 800 -1000). The antioxidative mechanisms of PCF were studied in this paper. It has been shown that superoxide anion free radical and hydroxyl free radical were scavenged by PCF (3%, 15%). The oils and fats peroxide values (POV) and the contents of MDA were also determined. The results showed that the percentage scavenging superoxide anion free radical were 11- 7% and 41. 8% ,scavenging hydroxyl free radical were 8-6% and 38. 4% respectively. It could decrease the oils and fats POV and the contents of MDA in 5d and 10d(P