ASPNJ(Acidic Serine Protease from Neanthes japonica)was first isolated and purified from Neanthes japonica in our lab.ASPNJ has both strong plasmin and proteolytic enzyme activities.The effects of ASPNJ on leukemia Jurkat cell were determined in order to provide an innovation direction for research and treatment of leukemia.1.ASPNJ has much strong proliferation inhibition effect on leukemic cells(Raji,U937,Jurkat)than other cells(4T1,Smmc7721,293T),thus leukemic cells are more sensitive to ASPNJ.ASPNJ could obviously inhibit Jutkat cell growth.The inhibitory rates were dosage and time dependent.2.ASPNJ enzyme activity is the necessary condition for its proliferation inhibition on Jutkat cells.While the effect of inhibition of ASPNJ on Jurkat cell may have some indirect mechanism,in addition to the direct effect that relies on its enzyme activity.3.Morphological changes,such as the cell membrane rupture,the chromatin condensation and nuclear pyknosis,etc were observed.Significant apoptosis induction effect of ASPNJ on Jurkat cell was detected with time and dose dependent manner.4.There had been a significant synergtic tumor suppression effect when vincristine was used in combination with ASPNJ to treat Jutkat cells.Killing tumor cells by different ways will greatly enhanced the effects of drugs.Reducing the dose of chemotherapeutic drugs can reduce the toxic and side effects.The anti-leukemic effect of ASPNJ may provide a new approach for the treatment of leukemia,and worth to be studied further.