In this paper,the peptide hydrolysates from bovine serum albumin(BSA)hydrolyzed by 2709 alkaline proteinase were analyzed by liquid chromatography coupled with quadrupole time-of-flight mass spectrometry,and then identified by the site-unspecified identification method of peptide mapping.The protein electrophoresis analysis indicated that all of BSA proteins were hydrolyzed by 2709 alkaline proteinase added at 0.1% level in 0.5 h,suggesting a strong proteolysis ability.The results of peptide mapping analysis indicated that the changes of peptide mapping were complex during the proteolysis process and different peptides displayed variable change features.The analysis of cleavage sites indicated that 2709 alkaline proteinase could be cleaved at almost any kind of amino acid sites,but their cleavage frequency were different.It suggested that besides broad site selectivity,2709 alkaline proteinase had a certain tendency of site selection in the proteolysis of BSA,with a significant selectivity tendency on leucine sites.The study provided a theoretic foundation for the rational use of 2709 alkaline proteinase in hydrolyzing proteins,and will help to improve the application of proteases in food industry in future.