Abstract: Objective:The anti-thrombus effect of fibrimolytic enzyme SNFE in Sipuculus nudus Linnaeus was studied. Methods:The effect of SNFE on the maximum aggregation rate of platelet induced by arachidonic acid(AA)in 5 min was measured by turbidimetry in vitro. Mice were randomly divided into blank group,model group,aspirin group(10 mg/kg),SNFE low-dose groups(4000 IU/kg)and high-dose(8000 IU/kg). Each group was given corresponding drugs intragastrically once a day and the body weight was recorded every 7 d. On the 12th day,except the blank group,the tail-thrombus model was established by subcutaneous injection of 0.8% carrageenan. After 48 h,the incidence of thromboembolism and the relative average thrombus length in tail were calculated. 2 h after the last drug delivered,blood was collected through pricking eyeball to measure prothrombin time(PT),activated partial thromboplastin time(APTT),thrombin time(TT)and fibronectin(FIB). Results:The maximum aggregation rate of platelet in 5 min induced by AA in low and high dose group was 20.2%±4.5% and 45.1%±2.5%,respectively. And there was significant difference between the high dose group and the blank group(P<0.01). The incidence of thrombosis was 90% in model group and low dose group,60% in high dose group. The relative average thrombus length in high dose group was shorter than that in model group(P<0.05). PT,APTT,TT of model group were shortened compared with blank group(P<0.05),while there was no significant difference in FIB,and high dose group significantly prolong the activated partial thrombin time(APTT)and thrombin time(TT)(P<0.05). Conclusion:The fibrinolytic enzyme SNFE would have antithrombosis effect.