Plasmin, microplasmin and plasminogen activators are used to treatment different thrombosis, disease characterized to formation of blood clots. This is a cause of death frequently associated with myocardial infarction, stroke, deep-vein thrombosis, and pulmonary embolism. Material and method: Microplasmin JG is a low-molecular-weight protein of two molecular chains of 29 and 35 KDa, obtained by plasminogen autolysis in alkaline medium, purified with affinity and anionic interchange chromatography. In vitro (fibrin and fibrin plate) and in vivo (carotid artery thrombosis in rabbits) assays were performed. Fibrinogen, platelets, thrombin time and hematocrit levels was measured before and after microplasmin infusion in rats. Results: Lysis fibrin clot showed a decrease in the weight (g) respect control (sodium borate buffer) (0,50 ± 0,02 vs 89,60 ± 3,19) in 25 min.  Microplasmin JG showed 25 UI/L activity in fibrin plate. Hematologic parameters showed no decrease either preinfusion and after 48 hours injection microplasmin JG treatment: fibrinogen (177 ± 2,18 vs 170,5 ± 3,75 mg%), platelets 464.083 ± 19.994 vs 509.333 ± 17.812 mm³) , thrombin time (42,41 ± 1,36 vs 39,80 ± 0,89 seg.) and hematocrit (44 ± 0,56 vs 46 ± 1,41 %).  Doppler in carotid artery thrombosis showed 100 % of reperfusion after 15 min. Conclusion:  Microplasmin JG is a two chain protein obtained with novel autolysis in alkaline medium, with excellent fibrinolytic effect in thrombosis artery without risk of hemorrhagic events.