The invention discloses a tuna fresh keeping method to solve a problem that present tuna fresh keeping methods reduce the quality of tuna. The method mainly comprises the following steps: 1, preprocessing tuna bodies; 2, immersing tuna in a composite fresh keeping agent; 3, carrying out surface air drying; and 4, packaging, and refrigerating. The composite fresh keeping agent comprises, by mass, 5-10% of mycose, 0.03-0.05% of nisin, 0.05-0.1% of konjak mannan, 0.1-0.3% of sodium phytate, 2-3% of calcium chloride, 0.2-0.5% of chitosan, 3-5% of disodium EDTA, 0.3-0.5% of sodium erythorbate, 0.3-0.5% of sodium citrate, and the balance of a propolis water extraction liquid. The fresh keeping method has the advantages of easy implementation, high efficiency, low cost, good fresh keeping effect, great prolongation of the fresh keeping time of tuna, maintenance of the original eating quality of tuna, good safety, facilitation of improvement of the economic benefit of ships, and suitableness for being popularized and applied.