Abstract: To investigate protective effects of squid ink polysaccharide ( SIP) on ovary injured by cyclophosphamide ( CP) .In this paper, female Kunming mice were used as model animals, which were administered orally with SIP as ovarian protection agent gavage to against ovarian failure caused by intraperitoneal injection of CP. The mouse body weight and ovarian index, levels of FSH, LH, E2 and T in serum, activities of SOD, GSH- Px and contents of GSH, MDA in ovary, histopathology, numbers of follicles were detected.Results showed that the negative roles of CP on ovary were significantly intervened by SIP, which recovered levels of FSH ( p < 0.05) , LH and E2 ( p <0.01) in serum, significantly increased activities of SOD ( p < 0.05) and GSH-Px ( p < 0.01) as well as GSH content ( p < 0.01) in ovary, and decreased MDA level ( p < 0.01) .Meanwhile, there were obvious increased in numbers of primordial follicles, primary follicles, mature follicle and the total number of follicles, and ovarian structure was made a distinct improvement.It was suggested that SIP could weaken ovarian damage caused by CP, which implyed a potential medicinal value of the marine bioactive polysaccharide.