The invention discloses monoesters, inner complex salts or monoester salts of hexahydro-²-acid, and application thereof as animal feed additives. The compounds of the present invention as shown in formula (I), (II) and (III) show low toxicity or non-toxicity to animals, and have higher stability and better growth promotion effects than those disclosed in other patents, which make them more suitable to be applied as growth promoters used in feed and have a very good application prospect in cultivation industry.
