The influences of propylene glycol mannate sulfate (PGMS) on experimental thrombosis and thrombolysis in vivo were studies after iv 8. 125, 6. 25, 12. 5 , 25mg/Kg in rabbits, and the effect of antithrombosis of PGMS was compared with that of heparin. The results showed that PGMS possessed remarkable effect of antithrombosis. In order to explore the mechanism of antithrombosis of PGMS, we studied the influences on the fibrinolytic and coagulant function of rabbits. The results showed that PGMS can pronouncedly prolong the prothrombin time (PT), thrombin time (TT), kaolin partial thromboplastin time (KPTT), and enhance the activity of antithrombin-III (AT -III). PGMS can cause a remarkable increase in fibrin degradation product (FDP) , shorten euglobulin lysis time (ELT) , and a decrease in the contents of fibrinogen and plasminogen activity. These results suggested that PGMS probably exert the antithrombotic effect by inhibiting coagulation and activating fibrinolysis.