This study investigated the effects of the partial substitution of dietary fish meal by corn-gluten meal on the growth, intestinal histology, and structure of intestinal bacteria in juvenile large yellow croaker () (mean initial weight 10.49 g±0.03 g). Six isonitrogenous (45% crude protein) and isolipidic (10% crude lipid) diets with various dietary protein levels (0%, 15%, 30%, 45%, 60%, and 75%, designated as FM, CGM15, CGM30, CGM45, CGM60, and CGM75, respectively) were formulated and fed to triplicate groups for 56 d. The results showed that the survival rate (SR), specific growth rate (SGR), and feed conversion ratio (FCR) were not significantly affected (>0.05). The observed intestinal histology (mucosa thickness, mucosal fold height, and goblet cell quantity) was not significantly affected in all of the groups (>0.05), but some epithelial cells in the CGM60 group were destroyed or rearranged in a disorderly manner and parts of the striated border and intestinal villus were destroyed, the mucosal fold height in the CGM75 group was lower than that in the other groups, and the density and numbers of mucosal folds decreased. An Illumina MiSeq high-throughput sequencing analysis of intestinal contents showed that the Chao1, Shannon, and Simpson indices, and Good's coverage in FM, CGM15, and CGM75 were not significantly affected (>0.05). The Firmicutes and Proteobacteria groups completely dominated the bacterial communities in juvenile , and genera were the most dominant bacteria in the microbial ecosystem. At the genus level, compared to the control group, the abundances of <0.05), the abundances of <0.05), and the abundance of <0.05). These results suggest that the optimal dietary-protein level is about 45% without adverse effects on growth, intestinal histology, and structure of intestinal dominant bacteria in juvenile .