Abstract:A study on inhibiting range and mechanism of the active product of S-5210-6 was launched for the sake of evaluating the application significance of the S-5210-6 for the biological control of plant diseases, and providing scientific basis for the follow up research on their development. The inhibiting range of the active product of S-5210-6 was studies by means of mycelium growth rate and inhibition zone in vitro and potted plant in vivo, respectively. The active product of S-5210-6 had a selective inhibition to pathogenic bacteria and a wide-range of inhibition to pathogenic fungi. It had a strong antagonistic action to 12 pathogens in vitro. To obligate parasite pathogens like Pseudoperonospron cubensis, the active product of S-5210-6 could not only hold back the infection of mycelia, but also heal the spot where infected by mycelia. The mechanism of the active product of S-5210-6 was studies. The active product of S-5210-6 had a strong inhibition of the mycelia growth and spore germination, and the pathogenicity of mycelia and spore was reduced after treated with the active product of S-5210-6. With the high concentration of the active product of S-5210-6, their pathogenicity was remarkably reduced.