The invention discloses a complex carbohydrate preparation for forage, a forage additive containing the complex carbohydrate preparation, and a use of the forage additive. The complex carbohydrate preparation comprises, by weight, 10-15 parts of fucose, 5-10 parts of galactose, 5-10 parts of N-acetylgalactosamine, 10-30 parts of glucosamine, 5-15 parts of N-acetylgalactosamine, 5-10 parts of glucuronic acid, 10-20 parts of mannose, 5-10 parts of sialic acid and 10-20 parts of xylose. The forage additive comprises, by weight, 65-140 parts of the complex carbohydrate preparation. The forage additive is added into basic daily forage according to a use ratio of 0.001-2% so that the forage for pregnant sows is obtained. The complex carbohydrate preparation improves sow constipation, improves pigling birth weight and sow lactation amount, provides a novel pregnant sow and lactating sow forage formula for actual production, improves production efficiency and culture benefits, has high safety, has no side effect, can adjust and balance various nutrients, prolongs a lactation period and is conducive to timely oestrus hybridization after sow weaning.