To comparatively study the effects of rPI-T1 with aprotinin and tranexamic acid, antifibrinolytic hemostatics currently used in clinical settings, by comparatively analyzing their inhibitory activities on plasmin, trypsin and kallikrein. Spectrophotometry was used, that was, OD405 was decreased by inhibiting protease hydrolysis of corresponding chromogenic substrates with inhibitors to measure corresponding activities and Ki values. Under the same measurement conditions, kallikrein inhibitory activity of rPI-T1 was approximately 1% of aprotinin. Tranexamic acid lysine analogues, on the other hand, had millimolar inhibitory concentrations because of different mechanism of action, i.e. noncompetitive inhibition. Due to the weak inhibitory effect of rPI-T1 on kallikrein, the potential side effects resulting from inhibiting kallikrein can be avoided. Characterized by high inhibitory concentration and poor specificity, tranexamic acid is prone to cause severe side effects.