Objective To analyze the effect of fisetin against venous thrombosis in rats.Methods Seventy SD rats were randomly divided into the following groups:sham-operation group,model group,fisetin 45 mg/kg,15 mg/kg,5 mg/kg groups,and aspirin group(47 mg/kg).The corresponding medication was administered by gavage once a day consecutively(the sham-operation group and the model group were given 0.5％carboxymethyl cellulose sodium solution with 10 mL/kg,respectively)for 7 consecutive days.One hour after the last administration,the rats were anesthetized,the lower part of the intersection of inferior vena cava and left renal vein was ligated with silk thread(no ligation in the sham-operation group),and the abdominal wall was sutured.Two hours later,the abdominal cavity was reopened,the other venous branches 1.5 cm away from the ligation site were closed with the artery clamp,and blood was collected from the abdominal aorta.The anticoagulant ratio of 3.8％sodium citrate∶whole blood was 1∶9.The venous thrombus 1 cm down from the ligation point of the intersection of inferior vena cava and left renal vein was cut and the thrombus was separated.The residual blood was dried with filter paper,weighed and recorded.Plasma was taken after anticoagulant blood centrifugation.The levels of plasma antithrombin-Ⅲ(AT-Ⅲ),protease C(PC),plasminogen(PLG),and plasminogen activator inhibitor(PAI-1)were detected by ELISA kits.Results Compared with the model group,the weight of thrombus in fisetin 45 mg/kg group and aspirin 47 mg/kg group decreased(P＜0.01).The content of AT-Ⅲ in three fisetin groups increased(all P＜0.05).The content of PC in fisetin 45 mg/kg increased(P＜0.05).The content of PLG and PAI-1 in fisetin 45 mg/kg group decreased(both P＜0.05).Conclusion Fisetin has the effect against venous thrombosis in vivo,and the effect is related to the upregulation of AT-Ⅲ and PC and the downregulation of PLG and PAI-1.