The invention relates to a preparation method of a novel medicine for inhibiting Cylindrocladium parasiticum, Colletotrichum corda and Phomopsis(Sacc.)Bubak. Indoleacetic acid, bromoethanol and carbendazim active compounds are used as synthetic raw materials to prepare an indoleacetic acid-carbendazim conjugate, which is the finish product, through a reaction. The invention also discloses nuclear magnetic resonance structure data, a hydrogen spectrogram and a carbon spectrogram of the novel compound. The compound has excellent antibacterial effects on the Cylindrocladium parasiticum, the Colletotrichum corda and the Phomopsis(Sacc.)Bubak.