The invention discloses a biological feed mainly composed of sugarcane tail leaf and a preparation method thereof. The sugarcane tail leaf is taken as the main raw material, bran, soybean meal, and fish meal are taken as the auxiliary materials, and then the materials are fermented by active 99 biological bacteria so as to produce the biological feed. The sources of raw materials are wide, the prices of raw materials are low, the manufacturing technology is simple, and the biological fertilizer is rich in various beneficial microbes, which can form strong dominant populations with the beneficial bacteria in the gastrointestinal tracts after the feed is eaten by animals, are capable of promoting protein synthesis in organisms, and can secrete and synthesize a great amount of amino acid, protein, vitamin, various digestion enzymes, micro growth promoting factors, and the like. At the same time, the active substances secreted by the beneficial microbes can prominently strengthen the immunity of animals, the using frequency of veterinary drug is greatly reduced, or the veterinary drug is not needed, and the quality of animals is greatly improved. The provided biological feed has the advantages of low cost, comprehensive nutrients, suitability for various animals, and good feeding effect.