The invention provides a Chinese herbal medicine feed additive for chickens and a preparation method and application thereof. The preparation method comprises the following steps: using a plurality of natural Chinese herbal medicines as raw materials, crushing the Chinese herbal medicines in the formulation, leaching the effective components in the Chinese herbal medicines, adding the prepared additive the amount of which is 0.5 to 4 weight percent of the feeding mass in daily feeds for various chickens, feeding the chickens after stirring evenly, and discontinuously adding feed in the whole process. The feed additive has the advantages that the raw materials are scientific and reasonable, the preparation process has strong operability, and the prepared additive has the characteristics of trace, high efficiency, favorable palatability, safety and non-toxicity, can promote growth and development of the chickens remarkably, advances the marketing time, and reduce feed cost; the feed additive has the functions of excellent bacteria resistance, stress resistance and immunity improvement, reduces the occurrence of plagues, realizes healthy and non-resistant breeding in the whole process, and can produce green and good-quality chicken products without medicament residues.