The invention provides a marine oligosaccharide-containing antifungal infection composition for pets, and belongs to the technical field of animal medicines. The invention opens up a new application of guluronic acid oligosaccharide, and the guluronic acid oligosaccharide serving as a synergist of antifungal drugs for pets can reduce the dosage of antifungal drugs such as azoles, polyenes and thelike, so that the toxic and side effects of the drugs, especially fluconazole, nystatin, amphotericin B and the like, are reduced. Especially, the guluronic acid oligosaccharide serves as a synergistof the antifungal drug for pets, so that the antifungal drug recovers the effect on drug-resistant fungi, pet fungal infection, especially drug-resistant fungal infection, is effectively treated, thetoxicity of the drug is reduced, the economic burden of pet medication is relieved, and the guluronic acid oligosaccharide has important feeding application value.