The invention discloses a method for preparing a cowfish stuffed specimen. The method comprises the following steps of (1) measuring each measurement of the cowfish, shooting the cowfish, dissecting, and peeling off the skin; (2) scraping the fat absorbed on the skin; (3) further defatting by a mixture of Na2CO3 (sodium carbonate) and corn flour; (4) immersing the skin in a 60% alcohol solution for seven days, then immersing the skin in a 40% alcohol solution for five days, and carrying out anti-corrosive treatment; (5) immersing the skin in a 0.5% Na2CO3 solution; (6) preparing specimen fillers according to the measured data and photos; (7) uniformly coating anti-corrosive paste on the inner surface of the skin to carry out anti-corrosive treatment; (8) sewing the specimen, and filling the filler; (9) shaping; (10) repairing; and (11) applying oil. The method disclosed by the invention has the advantages that the operation is simple, the defatting, anti-corrosive, mothproof and cracking-proof effects are good, the shaping is easy, and the prepared cowfish specimen is vivid and has no fishy smell.