The invention provides a feed detoxifier for livestock and a preparing method and application thereof. The feed detoxifier is prepared from, by weight, 30-50 parts of montmorillonite, 5-10 parts of gulcomannan, 5-10 parts of vitamin C, 20-30 parts of medical stone and 1-10 parts of acetic bacteria yeast freeze-dried powder. Through detoxification synergetic action of different components, adsorption, degradation and detoxification are well achieved. The feed detoxifier is free of toxin or harm to organisms and free of residues, can adsorb and degrade toxin, and can also promote livestock to discharge mould and mycotoxin after entering the body of livestock, so that harm to livestock caused by mycotoxin is reduced greatly.