The activity of tPA and PAI of rabbits receiving different dosages of the Svate -3 were assayed with special substrata decomposition method. It was found that after Svate- 3 infusion, the activity of tPA increased but the activity of PAI decreased and it was related to the dosage and the speed of administration. The size of fibrinolysis in blood fibrin plate was in positive correlation to the activity of t-PA(r=0. 861,P