Abstract: AimTo select higher thrombolytic and lower toxic single component of earthworm fibrinolytic enzymes (EFE). MethodsEFE containing total components were obtained by affinity chromatography from Eisenia fetida. Using ion-exchange chromatography to separate three main components EfP-0-2, EfP-I-1 and EfP-I-2 from EFE, their thrombolytic activity and toxicity were compared with EFE. ResultsAmong these components, EfP-I-1 had higher thrombolytic activity in vitro. When 4.5 mg·kg^-1 of these components were injected, the contents of fibrinogen in rat serum were not affected , but only EfP-I-1 exhibited distinct thrombolytic activity. When 6.0 mg·kg^-1 of them were injected intravenously, the bleeding time was not evidently delayed only by EfP-I-1. The acute toxicity test showed that the LD₅₀ of EfP-I-1 was higher than EFE by 2.17 times. ConclusionBecause of distinct thrombolytic activity, lower toxicity in vivo, higher content in EFE and easy to purify, EfP-I-1 was adapted to be developed as a single component medicine for treating thrombus.