Abstract: This study was aimed to optimize the extraction process of sea cucumber sperm polysaccharide( SCSP),and evaluate its antitumor activity in vitro.After enzyme screen and single factor experiments,factors such as enzyme dosage,extraction temperature and extraction time were taken into account to perform response surface experiment optimization according to polysaccharide yield. The in vitro growth inhibition effects of sea cucumber sperm crude polysaccharide( SCSCP) and its purified components( SCSP A1,SCSP A2) on human cervical cancer Hela cells and human liver cancer Hep G2 cells were measured with MTT assay.The results showed that the optimum extraction conditions of SCSCP were as follows: papain,enzyme dosage of 3%,extraction temperature of 49 ℃,extraction time 6 h.Under these conditions the yield of SCSCP was 10.643‰.The MTT results indicated that SCSCP and its purified components inhibited the survival rates of Hela cells and Hep G2 cells.SCSP A2 exhibited a higher inhibition rate than SCSP A1.At the concentration of 10 mg / m L,inhibition rates of SCSP A2 on Hela and Hep G2 at 72 h were 80.28% and 83.11%,respectively,implying that SCSP had a remarkable in vitro antitumor activity.