Abstract: Water flow velocity is one of important eco-environment factors which affects the fish growth. In order to explore the function and expression of related genes of Plectropomus leopardus under different flow velocity, we conducted a transcriptome analysis of liver tissue of P. leopardus under different flow velocity by RNA-seq technology. We selected the fish fry of P. leopardus with identical size from the same breeding batch and cultured them for 150 d with water flow velocity of 0.1 m·s⁻¹ (Low flow velocity, LFV) and 0.4 m·s⁻¹ (High flow velocity, HFV). Then, we conducted a transcriptome analysis on the liver so as to investigate the difference of gene expression patterns with different flow velocity. We had obtained a total of 1 977 differentially expressed genes (DEGs) by transcriptome analysis (999 up-regulated and 978 down-regulated for LFV-HFV, respectively). The GO functional annotation reveals that 1124 DEGs were annotated in Gene Ontology Consortium and assigned to 56 functional terms. KEGG pathway analysis shows that 573 DEGs belonged to 154 pathways, and PPAR signaling pathway was most significantly enriched. Histological observation of livers of the tested fish indicates that the difference in fat contents between LFV and HFV group was significant, and the fat content was obviously higher in LFV than in HFV (P<0.05). According to the transcriptome analysis, we excavated many DEGs under different flow velocity, which provids technical support for further research on the molecular regulation mechanism of adaptability to change in flow velocity of P. leopardus.