Disclosed are an antimycin compound and a preparation method and use thereof. The preparation method comprises: fermenting a marine actinomycete (Streptomyces sp.4-7) with a preservation number CCTCCNO: M2020953 to obtain a fermented product and soaking and extracting the fermented product with ethyl acetate to obtain a crude extract; and carrying out separation and purification by normal-phase silica gel column chromatography, reversed-phase MPLC, and semi-preparative reversed-phase high-performance liquid chromatography. The invention has the advantages of resistance against Botrytis cinerea and Penicillium citrinum.