Abstract: Considering that black pepper extracts inhibit food spoilage and food pathogenic bacteria,the antimicrobial mechanism of four different organic phases of pepper extract against Bacillus subtilis were explored.The antibacterial mechanism of pepper extract was elucidated by analyzing pyruvic acid content and transaminases activities of the target bacteria. The extract significantly increased pyruvic acid concentration in bacterial solutions,especially with the treatment of ethyl phase,the concentration of pyruvic acid were up to0.527 g / L. And the activity levels of ALT and AST in the cultures of bacterial cell were increased severely with adding pepper extracts,and the highest enzyme activity was 28.62 and 49.29 Kar U,respectively. The results indicated that pepper extracts inhibited the metabolic and energy synthesis of Bacillus subtilis,which consequently affected the growth and metabolic of Bacillus subtilis.