Abstract: Objective:The antibacterial effect and mechanism of N-butanol extracted from Clerodendrum philippinum var. simplex(ECP)was studied. Methods:The sensitivity of Staphylococcus epidermidis,Staphylococcus aureus,typhoid bacillus and Pseudomonas aeruginosa to ECP were determined by disk diffusion method and broth dilution method. And the antibacterial effects and mechanisms of ECP on S.aureus were studied in the aspects of cell wall,cell membrane and morphological structure. Results:ECP had antimicrobial activity on all of the four test bacteria. Among which,it was the most powerful for S. aureus,and the minimum inhibitory concentration(MIC)and the minimum bactericidal concentration(MBC)were both 0.50 mg/mL. After S.aureus was treated with ECP,the leakage of content from intracellular,cellular oxidative damage and apoptotic were all increased obviously. At the same time,the activities of dehydrogenases and protein content were both decreased significantly. Scanning electron microscope(SEM)results indicated that the whole cell was damaged severely. Conclusions:The targets of ECP inhibition on the growth of S.aureus might be the cell membrane,cell wall,key enzymes of tricarboxylic acid(TCA)cycle,proteins and genetic material and so on. And Clerodendrum philippinum had specific potential for natural food additives.