The invention relates to the technical field of feed additives, in particular to a mixed fish feed containing a feed additive and a preparation method of the feed. The feed additive is a honeysuckle decoction residue alcohol extract powder, and the raw material is honeysuckle decoction residues which are subjected to Soxhlet extraction, and the honeysuckle decoction residues are subjected to alcohol-microwave extraction. The effective components of the honeysuckle decoction residue alcohol extract powder include 28-35 mg/g chlorogenic acid, 8-15 mg/g luteolin, 4-10 mg/g quercetin and 5-13 mg/grutin. The mixed fish feed is a mixture prepared by uniformly stirring a basic fish feed and the feed additive, and is suitable for the culturing of fishes in light eutrophic water bodies. The mass ratio of the basic fish feed and the feed additive is 1000:8 to 1000:15. The light eutrophic water bodies refer to water bodies with a comprehensive trophic state index of 50-60. The feed improves thequality of fishes in light eutrophic water bodies while improving the comprehensive utilization value of the honeysuckle decoction residues.