Abstract: Objective: To study the antithrombotic effect and the effect on platelet activity of fibrinolytic enzyme from Lyophyllum ulmarium.Methods: The carotid arterial thrombosis model was induced by ferric chloride in rats,and then the thrombus weight was detected.The expression of CD62 p on the platelet were applied by flow cytometric analysis,and the levels of p- selectin,v WF,platelet glycoprotein Ⅱb / Ⅲa( GPⅡb / Ⅲa),TXB2 and 6- keto- PGE1α,in plasma were measured.Results: Compared with the model group,fibrinolytic enzyme from Lyophyllum ulmarium reduced thrombus weight,suppressed the expression of CD62 p,and reduced the contents of P- selectin,v WF,platelet glycoprotein GPⅡb / Ⅲa and TXB2.However,there was no significant difference in the 6- keto- PGE1αlevel.Conclusion: Fibrinolytic enzyme from Lyophyllum ulmarium had an antithrombotic activity,and the mechanism might be due to inhibition of platelet activity.