OBJECTIVE： To study the improvement effects of fibrinolytic enzyme from Sipunculus nudus （SNFE） on hemorheology disorder and vascular endothelium injury in naked acute blood stasis model rats. METHODS： SD rats were randomly divided into control group， model group， aspirin group （100 mg/kg） and SNFE high-dose and low-dose groups （2 500， 5 000     U/kg）， with 10 rats in each group. They were given relevant medicine intragastrically once a day， for consecutive 7 d. One hour after the 6th day of administration， except for control group， other groups were given adrenaline hydrochloride 0.8 mg/kg subcutaneously， and then the acute blood stasis model was induced by ice-water bath. Blood was collected from abdominal aorta 2 h after the next day. Blood rheological parameters such as whole blood viscosity （high， medium and low shear rate）， plasma viscosity， hematocrit， erythrocyte aggregation index and erythrocyte deformability index were measured by automatic rheometer. The contents of NO and ET-1 in plasma and their ratio were determined by ELISA， and the damaged degree of vascular endothelium were observed by HE staining. RESULTS： Compared with control group， whole blood viscosity of high， medium and low-shear rate， plasma viscosity， erythrocyte aggregation index and ET-1 content were increased significantly in model group， while erythrocyte deformability index， NO content and NO/ET-1 ratio were decreased significantly， with statistical significance （P＜0.05 or P＜0.01）. Compared with model group， whole blood viscosity of high， medium and low-shear rate， plasma viscosity， hematocrit， erythrocyte aggregation index and ET-1 content were decreased significantly in SNFE high-dose groups. Erythrocyte deformability index， NO content and NO/ET-1 ratio were increased significantly， with statistical significance （P＜0.05 or P＜0.01）. In SNFE low-dose group， erythrocyte deformability index and NO/ET-1 ratio were increased significantly， while ET-1 content was decreased significantly， with statistical significance （P＜0.05 or P＜0.01）. Vascular endothelial staining showed that compared with control group， the structure of aorta layers in model group was loose and disordered， the endothelial defect was incomplete， the vacuoles increased， and the endothelial damage was obvious. The endothelium of rats in each administration group was damaged to varying degrees， but the degree of injury was lighter than in model group. CONCLUSIONS： SNFE can improve hemorheological abnormalities and vascular endothelial injury in rats with acute blood stasis.