The invention discloses a slowly-released compound acidifier for poultry and livestock feed, a preparation method thereof and feed containing the same. The compound acidifier comprises the following compositions in part by weight: 30 to 80 parts of complex organic acid, 15 to 50 parts of supplementary materials and 5 to 20 parts of coating agents. The complex organic acid is citric acid, fumaric acid, malic acid, lactic acid, linoleic acid, crataegolic acid, ursolic acid, chlorogenic acid, glycyrrhizic acid and oleanolic acid, and the supplementary materials are silicon dioxide, hydroxypropyl methylcellulose and ethyl cellulose. The acidifier is scientifically proportioned, has strong efficiency and is long-acting and slow-releasing, nutrients in the feed are free from being damaged, the acidifier has good fluidity and is easy to be uniformly mixed with the feed, the digestive absorption of nutrients can be promoted, the conversion rate of the feed can be improved, the productivity of poultry and livestock can be improved, the time for domestic animals for sale can be effectively shortened, the health of gastrointestinal mucosa of the animals can be protected, the immunologic function of the animals can be strengthened, and diseases can be prevented.