To study the effects of non-starch polysaccharide-degrading enzymes on true amino acid and nutrient metabolic rates of corn by-products, a complete randomized design and three metabolic test periods had been taken, and 56 healthy adult yellow-feathered roosters with an average body weight of (2.5?0.2) kg were randomly divided into 7 groups with 8 replicates in each group and 1 rooster in each replicate. The roosters were force-fed with a single raw material and the material with non-starch polysaccharide-degrading enzymes to determine the true amino acid metabolic rates of corn and its by-products before and after the enzyme addition. Results showed that before the enzyme addition, the average true amino acid metabolic rate of corn was the highest, and the lowest one was germ (no spray, from Jining). After the enzyme was added, the true amino acid metabolic rates of corn by-products were between 70.77% to 99.29%, and the enzyme increased the true amino acid metabolic rates of corn by-products by 0.96% to 3.52%. The true metabolic rates of many amino acids in corn and corn gluten meal [crude protein (CP) 50% and CP 55%] were significantly increased by the supplementation of the enzyme (P<0.05). And the effective nutrient improvement values (ENIV) of true available amino acid contents of corn by-products were in the range of 0.03 to 1.87 g/kg, the highest was corn gluten meal (CP 55%), and the lowest one was corn fiber feed. The supplementation of the enzyme can improve the metabolic rates of true CP, dry matter (DM) and ether extract (EE) of varieties of corn by-products (P>0.05), and for some by-products it could significantly increase the true metabolic rates of DM and CP (P<0.05). The enzyme could also significantly enhance the true crude fiber (CF) metabolic rate of all corn by-products (P<0.05). Generally speaking, complex non-starch polysaccharide-degrading enzymes can improve the true amino acid and nutrient metabolic rates of corn and its by-products.