The  study  investigated  dietary  effects  of replacing  fish  meal  (FM)  with Clostridium  autoethanogenum powder (CAP) on growth, flesh quality and metabolomics of largemouth bass (Micropterus salmoides). The control diet contained 350 g/kg FM, and then dietary FM was decreased to 300 g/kg, 250 g/kg, 200 g/kg, 150 g/kg and 100 g/kg by CAP inclusion, respectively (FM-30, FM-25, FM-20, FM-15, FM-10). Then, the six diets were fed to largemouth bass with initial body weight of 110 g for 56 days. The high CAP inclusion (FM-10) decreased specific growth rate, flesh collagen, flesh hardness and increased feed conversion ratio (P < 0.05), but no significant difference was found in feed intake among all the groups. FM-25 and FM-10 groups presented higher flavoring amino acids contents and better performance in sensory evaluation than the control group (P < 0.05), and FM-10 group also showed better values in electronic tongue evaluation. The differential metabolites in FM-25 and FM- 10 groups were found to be involved in lipid, amino acid and protein metabolism. In conclusion, in a basal diet containing 350 g/kg FM, 150 g/kg dietary FM could be successfully replaced by CAP, while higher FM substitution decreased the flesh collagen content and flesh hardness of largemouth bass.