The invention discloses a preparation method of a marinated duck, which comprises the following process steps of material selection, trimming, material mixing, curing, drying, frying, boiling, cooking, quantitative dividing, vacuum packaging, high-temperature sterilization, cooling, external packing, inspection and finished product delivery, wherein the ratio of salt, peppers, fried aniseeds added in the curing process is 100:(0.4-0.6):(0.8-1.2); in the boiling process, the boiling stewing materials comprise the following components in percentage by weight: 0.8 to 1.2 percent of salt, 0.2 to 0.4 percent of monosodium glutamate and 0.8 to 1.2 percent of cooking wine, and the materials are stewed for 30 to 40 minutes at the temperature of between 93 and 100 DEG C; and the high-temperature sterilization process comprises the steps of: putting the vacuum-packaged cooked duck into a high-temperature sterilization boiler, adjusting the pressure in the boiler to be between 0.15 and 0.25 kPa, then raising the temperature to be between 112 and 121 DEG C in 4 to 6 minutes, and performing constant-temperature sterilization for 25 to 30 minutes. The preparation method is suitable for preparing the marinated duck.