The invention provides a feed additive for improving liver mitochondrial function of weaned piglets with intrauterine growth retardation and a preparation method and applications thereof. The feed additive of the present invention mainly comprises the following raw materials: blueberry anthocyanin, okra polysaccharide, olive leaf extract, malic acid, alpha-lipoic acid and a carrier. In the feed additive of the present invention, the components are all natural products, are safe, and do not cause residue. The synergistic compatibility existing between the components can improve liver mitochondrial function and promote the growth and development of weaned piglets with IUGR (intrauterine growth retardation) with good and stable effects.