Selenium yeast(SY)and tea polyphenols(TP)belong to high-quality natural antioxidants.As an organic selenium source,SY has the effects on both promoting growth and improving product quality.TP is a term for polyphenols in tea,which is helpful to induce growth,improve product quality and enhance immunity.In the present study,a two-factorial and three-level experiment was designed to evaluate the effects of dietary SY,TP and their combination on the growth performance,the nutritional composition in muscle and the ability to resist Aeromonas hydrophila in juvenile Wuchang bream,Megalobrama amblycephala[mean weight(1.75±0.01)g].Totally nine semi-purified diets were formulated to provide graded levels of SY 0,0.25,0.50 mg/kg and TP 0,50,100 mg/kg.After 60 days' feeding,the growth performance,muscle composition,biochemical parameters of serum and liver,related gene transcription in the hypothalamus-pituitary-growth axis as well as survival rates after being infected with A.hydrophila were investigated.The results showed that dietary SY and TP significantly improved the weight gain rate(WGR),specific growth rate(SGR)and the content of protein in muscle(P<0.05),while reduced the food conversion ratio(FCR)significantly(P<0.05).Both dietary SY and TP significantly enhanced the growth performance by upregulating the mRNA expression of growth related genes in the hypothalamus-pituitary-growth axis.The difference is that SY mainly upregulated the mRNA expression of MaGH and MaIGF-I significantly(P<0.05),whereas TP enhanced the transcription of MaGHR₂ and decreased the mRNA level of MaIGF-I significantly(P<0.05).Consequently,dietary SY significantly enhanced the contents of GH and IGF-Ⅰ in the serum,whereas TP decreased serum IGF-Ⅰ levels significantly(P<0.05).No significant interaction effect of dietary SY and TP on serum GH and IGF-Ⅰ was observed in juvenile Wuchang bream(P>0.05).Both dietary SY and TP significantly enhanced the crude protein content in the muscle(P<0.05).And there was no significant interaction effect of dietary SY and TP on the content of the crude protein in the muscle(P>0.05).Both dietary SY and TP could improve the ability to resist A.hydrophila.And there was an interaction effect of SY and TP on the ability to resist A.hydrophila.In light of the above,it could be concluded that a basal diet supplemented with 0.50 mg/kg of SY and 50 mg/kg of TP could help keep better growth performance and disease resistance in juvenile Wuchang bream.