The invention discloses application of p-thymol and salt or ester derivatives thereof in an animal feed additive. P-thymol is an isomeride of thymol with the chemical name of 3-methyl-4-isopropyl phenol. The salt derivatives of p-thymol comprise salts formed by p-thymol and metal ions, p-thymol ammonium formed by p-thymol and ammonia, resin salts formed by p-thymol and negative ion resins and the like and the ester derivatives of p-thymol comprise esters formed by p-thymol and different carboxylic acids. The application firstly discovers that p-thymol and the salt derivatives or the ester derivatives thereof have stronger antibacterial activity, lower volatility, higher safety and lower thrill compared with thymol and carvacrol. When being taken as the additive of the animal growth promoting feed, p-thymol and the salt derivatives or the ester derivatives thereof have better palatability and growth promoting effect compared with thymol or carvacrol.
