The invention relates to a feed additive capable of regulating the energy metabolism of organisms and improving oxidation resistance, as well as a preparation method and application of the feed additive, and belongs to the field of feeds. The feed additive comprises the following raw materials of short-chain keto acid, glutamine, N-methylguanidinoacetic acid, L-carnitine, plant polysaccharide, phytase and potassium diformate. Through the adoption of the feed additive, the energy metabolism of the organisms of pigs and the health of intestinal tracts of the pigs are regulated, so that the diarrhoea rate of the pigs can be notably reduced, and the growth properties, the oxidation resistance capacity and the immunity of the pigs can also be notably improved. The preparation method of the feedadditive comprises the following steps of enabling the potassium diformate to dissolve in water, and then adding the short-chain keto acid, the N-methylguanidinoacetic acid, the plant polysaccharide,the glutamine, the L-carnitine and the phytase. The preparation method is simple and easy to operate, the activity of all the raw materials can be reserved to the maximum extent, and the synergisticeffects can be improved. When the feed additive is used for preparing a pig feed, the diarrhoea rate of the pigs can be effectively reduced, and the growth properties, the oxidation resistance capacity and the immunity of the pigs can be improved.