The invention provides a chicken feed additive free of antibiotics and hormones. By utilizing pure natural Chinese herbal medicine plants, broiler chickens can resist diseases and be kept healthy. Besides, the natural sour, sweet, bitter and hot tastes of these plant product additives cater to feeding hobbies of the broiler chickens, and the adaptability and utilization rate of feed can be improved. The chicken feed additive comprises, by weight parts, 1800-2500 parts of tangerine peel, 1200-2000 parts of herba houttuyniae, 1500-2000 parts of herba andrographitis, 1500-2000 parts of folium isatidis, 2000-2500 parts of folium artemisiae argyi, 2000-2500 parts of pine needle, 1000-1500 parts of radix isatidis, 1000-1500 parts of radix sophorae flavescentis, 1000-2000 parts of purslane, 800-1000 parts of dandelion, 500-800 parts of astragalus, 500-1000 parts of radix glycyrrhizae, 500-1000 parts of folium perillae, 500-1000 parts of garlic, 500-800 parts of cinnamon, 250-500 parts of clove, 300-400 parts of ginger, 250-300 parts of anise and 200-250 parts of pepper.