The invention relates to sipunculus nudus plasmin which is extracted from sipunculus nudus and has double activities of directly dissolving fibrin and kinase. The sipunculus nudus has the materialization performances that the molecular weight ranges from 27000 to 35000, the isoelectric point ranges from 4.5 to 7.0, the dissolving activity of fibrin varies little within the temperature range of 30to 70 degrees centigrade, and the stability range of the pH value ranges from 5.0 to 9.0. The sipunculus nudus plasmin has double activities of directly dissolving the fibrin and the kinase, simple extraction process, low preparation cost and easily obtained materials, can be developed into vein injection, contains the plasmin for directly degrading thrombus and is expected to have better effect on treating periphery arterial occlusion and deep vein thrombosis in a conduit-assisted thrombolytic therapy.