Abstract: Ducklings were randomly assigned to four treatments and fed corn-soybean basal diets and diets supplemented with 50 mg/kg olaquindox, 5 mg/kg. Flavomycin, 80 mg/kg oxytetracycline + 50 mg/kg arsanilic acid,respectively. The results showed that,the weight gain was increased by 4.07%, 7.77%, 6.49% ( P 0.01) respectively and the economic benefit of gain was increased 3.17%, 29.76%, 12.68% respectively compared with the control. It was suggested that. Flavomycin could be used as an ideal feed additive for promoting growth of ducks.