Abstract: The antibacterial activity of Zanthoxylum armatum DC Prodr.oil against common bacteria and yeasts were tested by using inhibition zone experiment and tube double dilution method to determine minimum inhibitory concentration ( MIC) and minimum bactericidal concentration ( MBC) . The antibacterial effect of oil against mould were tested by using growth rate method. The oil was also studied for its stability to thermal treatment, ultraviolet and p H.The results showed that Zanthoxylum armatum DC Prodr.oil had certain effect on restraining the growth of all the bacteria in the test.While the antibacterial effect of oil extracted from absolute ether were stronger than cold presssed oil.