The invention discloses a mold removal agent for feed and a preparation method and a feed additive thereof, belonging to the field of feed additives. The mold removal agent contains modified montmorillonite, yeast cell walls, chitosan, citric acid and Chinese herbal medicinal ingredients, wherein the Chinese herbal medicinal ingredients are prepared from poria cocos, rhizoma alismatis, grifola, cinnamomum cassia, rhizoma atractylodis macrocephalae and rhizoma imperatae. The mold removal agent can be used for removing mold for feed raw materials such as corn and grains and compound feed polluted by mycotoxin so as to prevent livestock and poultry from having various diseases as the livestock and poultry eat the feed polluted by the mycotoxin. The mold removal agent can reduce the absorption of the mycotoxin in the bodies of animals and meanwhile enhances the detoxification ability and the self regulating function of the bodies of animals, achieves the purpose of treating both symptoms and root causes. The mold removal agent has the characteristics of significant curative effect, safety in use, specific effect, stable preparation, controllable quality and simple preparation process, is suitable for industrial production and is convenient to feed.