The invention discloses a livestock feed additive, in particular a broiler chicken feed additive and a preparation method thereof. The broiler chicken feed additive is characterized by being prepared from hawthorn, malt, medicated leaven, root of straight ladybell, fragrant solomonseal rhizome, Codonopsis pilosula, Chinese angelica, tangerine peel, astragalus, ginger and Chinese date. The broilerchicken feed additive prepared by the method is used for promoting the growth and development of broiler chickens. The hawthorn has the effects of promoting digestion and relieving stasis; the malt has the effect of promoting digestion and regulating the middle warmer; the medicated leaven serving as the main medicament has the effects of promoting digestion and removing food retention; the root of straight ladybell has the effect of nourishing the stomach to improve the production of body fluid; the fragrant solomonseal rhizome serving as an auxiliary medicament has the effect of nourishing yin to moisten dryness and helping to produce saliva and slake thirst; the Codonopsis pilosula has the effect of replenishing qi to invigorate the spleen; the Chinese angelica has the effect of enriching the blood; the tangerine peel can enliven the spleen by regulating vital energy and alleviating middle energizer; the astragalus serving as an assistant medicament can tonify middle-Jiao and Qi; and the ginger and Chinese date, which serve as guide medicaments, can tonify the spleen and appetize. The broiler chicken feed additive can promote feed intake and percentage of weight growth of broiler chickens, reduce feed-to-meat ratio and improve breeding economic benefit. The additive is prepared from pure traditional Chinese medicine extracts and is free medicinal residual and safe and reliable.