Abstract: This paper reviews the serine proteases’ structures,functions,protein engineering,expression system,and applications.Serine protease is a group of proteolytic enzymes that are important for its potential applications.All serine proteases have serine,histidine and aspartic acid in their active domain,and same catalytic mechanism.The members in the serine protease super family serve a wide range of physiological functions,especially in the pathogenesis of many diseases and intracellular signal transduction.Any minute alternations in their structures can result in significant functional changes.