| To study the effect of lipid level on the expression of carnitine palmitoyl transferase I (CPT1) gene in the body tissues of largemouth bass and the expression patterns of different growth stages. Three different isonitrogenous diets with graded levels of lipid [6% (low lipid), 12% (medium lipid) and 18% (high lipid)] were feed to largemouth bass with the initial weight of 23.60 ± 1.26g. Tissue samples of liver, intestine, kidney and muscle were taken on the 30th, 60th and 90th day of feeding, and the 18S was used as the internal reference gene. The real-time PCR experiment was performed with CPT1 specific primers, and the relative expression data of CPT1 gene was obtained by 2-△△ct method. The results showed that the expression level of CPT1 gene was highest in the liver (P<0.05), followed by intestinal and kidney (P<0.05), and the expression level was lower in silk, heart, muscle, stomach, brain and spleen; Under different fat levels, the expression of CPT1 increased with the increase of lipid level; in different growth stages, the expression of CPT1 increased with the prolongation of feeding time. The results showed that the increase of lipid level and feeding time would induce the expression of CPT1 gene, and CPT1 gene may played a certain role in the decomposition of fat in the largemouth bass.