Protein C activator from Agkistrodon halys halys venom has been purified by ion-exchange and gel-filtration chromatography. The purified enzyme consists of a single peptide chain with molecular weight of 34 kD. Its pH-optimum was the range of 7,5-8,0. The enzyme was inhibited by DFP, benzamidine, PMSF, EGTA. Protein C activator was as effective as Protac (Pentapharm AG, Switzerland) for determination of protein C level in blood plasma using APTT test and protein C chromogenic substrate.