The invention relates to the technical field of aquatic product processing and storage, which solves the problems of serious fat oxidation, difficult preservation of product flavor and more juice lossin the traditional mackerel processing and storage process, the invention provides a method for cooking mackerel fillets in vacuum at low temperature, which comprises the following steps: (1) leaching mackerel fillets with water, draining the material, adding a composite antioxidant, stirring uniformly the materials, and performing standing at low temperature; (2) putting the material into a cooking bag, performing vacuum sealing, and performing low-temperature cooking treatment; and (3) cooling and storing. According to the method, the mackerel meat is pretreated by utilizing the synergisticeffect of a compound antioxidant, so that a relatively good oxidation control effect is achieved, and the fat oxidation is effectively avoided; a low-temperature vacuum cooking technology is adopted,so that the flavor and juice of mackerel products are kept; the cooked mackerel fillet products are unique in flavor and long in shelf life, and the phenomenon of the fat oxidation is not prone to occurring in the storage process.