All of the thrombolytic agents currently approved for use in humans are plasminogen activators, the application of which is limited by bleeding complications at vascular injury sites and plasminogen content in the thrombus. Plasmin is rapidly neutral-ized in the circulation by α2-antiplasmin and tolerated without bleeding. With the application of catheter-based delivery, the unique bio-chemical properties of plasmin make it a safe and effective direct fibrinolytics. Plasmin derivatives, including miniplasmin,Δ-plasmin and microplsmin, display more thrombolysis efficacy and better hemostatic safety in preclinical study and clinical trials. This review sum-marizes the current information on plasmin and its derivatives, including the advances on biochemical properties, preclinical and clinical trials.