The invention relates to a composite feed additive capable of improving liver mitochondria function of jewfish as well as a preparation method and application of the composite feed additive, and belongs to the field of feeds. Each 100 parts by weight of the composite feed additive comprises the following components in parts by weight of 6-10 parts of manganese chelate methionine, 2-6 parts of copper chelate methionine, 30-50 parts of berberine, 20-30 parts of creatine, 0.5-2 parts of red Fife yeast and the balance of a carrier. The raw materials of the composite feed additive are safe, harmless, and free from residues, and create condition for production of green feeds and aquatic products. According to the preparation method of the composite feed additive, the raw materials are mixed in compounding ratio. The preparation method is simple, good in condition controllability, and good in stability, and has favorable application prospects. The composite feed additive is applied to preparation of the feed for jewfish, so that the liver mitochondria antioxidant ability and the mitochondrial respiratory chain function of the jewfish can be improved, and the mitochondria oxidative damagecan be reduced.