Serine proteases are widely found in snake venoms. They have variety of functions including contributions to hemostasis. In this study, five serine protease were cloned and characterized from two different cDNA libraries. Factor V activator (RVV-V), alpha fibrinogenase (RVAF) and beta fibrinogenase (RVBF) from Russell’s viper (Daboia russelli siamensis), and plasminogen activator (APL-PA) and protein C activator (APL-C) from Agkistrodon piscivorus leucostoma. The snake venom serine proteases were clustered in phylogenetic tree according to their functions. KA/KS values suggested that accelerated evolution has occurred in the mature protein-coding regions in cDNAs of snake venom serine proteases.