The invention discloses a black soybean milk flavor and a preparation method and an application thereof. The flavor comprises isovaleric aldehyde, methyl alcohol, isopentyl alcohol, hexanal, 2-methylpyrazine, furfural, trans-2-hexenal, furfuryl alcohol, hexyl alcohol, 2-heptanone, heptanal, 2-acetylfuran, 2, 5-methylpyrazine, 2, 3-dimethyl pyrazine, trans-2-heptenal, 5-methyl-furfural, benzaldehyde, heptanol, 1-octen-3-alcohol, 2-pentyl-furan, caprylaldehyde, 2-acetyl thiazole, trans-2-octenyl aldehyde, octanol, nonanal, capraldehyde, trans,trans-2,4-nonadienal, trans-2-decenal, 2-undecanone,trans,trans-2,4-heptadienal, trans-2-undecenal and propylene glycol. The method comprises the following steps: evenly mixing the above constituents, stewing and curing for 15 days, subpackaging to obtain the black soybean milk flavor. The flavor has convenient raw materials sources, mild fragrance and high naturalness, and is applied to preparing the beans products, is especially used for preparing black soybean milk beverage, not only can enhance mouthfeel, but also can better cover soil mildewed flavor brought by beans in basic materials.