Abstract: This paper explored the antibacterial effect and mechanism of natural plant extract oil on vegetable pathomycete.It not only measured the antibacterial activity and periods of oregano oil for botrytis cinerea and phytophthora capsici by using traditional Chinese medicine (TCM) bacteriostatic experiment method ,but also studied the resistance of oregano oil under different conditions.It turned out that oregano oil have obvious inhibitory effect on the above two kinds of fungi,and the bacteriostatic effect and concentration were positively correlated,the developing 3d EC50 were 0.4076、0.4626 mg/ml separately,and the bacteriostatic period was mainly in fungal rapid growth period so that the rapid growth phase could lag.Resistance experiments showed that these two kinds of pathogenic bacteria strains were extremely sensitive to oregano oil.