The invention provides a feed additive for resisting heat stress as well as a preparation method and application of the feed additive, and relates to the field of feed additives. The feed additive forresisting heat stress is prepared by mixing the following raw materials in parts by weight: 225-280 parts of potassium sulphate, 122-165 parts of sodium bicarbonate, 16-20 parts of calcium hydrogen phosphate, 180-220 parts of vitamin C, 84-100 parts of vitamin E, and 320-375 parts of a hesperidin extract. The feed additive can help animals to resist heat stress, the production performance of livestock and poultry is improved, and the feed additive is convenient and effective. The preparation method of the feed additive for resisting heat stress comprises the steps of mixing the raw materialstwice, and the method is simple. The feed additive for resisting heat stress is used and added to a feed or drinking water of the livestock and the poultry so as to improve the heat stress of the livestock and the poultry.