Abstract: To investigate the mechanism of peroxisome proliferator-activated receptor-γ coactivator-1 beta(PGC-1β)in the energy metabolism of grass carp Ctenopharyngodon idella,the partial cDNA of PGC-1β was cloned,and tissue expression and nutritional regulation were investigated.The partial cDNA was 885 bp (GenBank number:KM580493.1),encoding a polypeptide of 293 amino acids,compared to zebra fish,it showed 81% homology.Quantitative real-time PCR showed that highest PGC-1β mRNA expression was detected in brain, followed by intestine and liver.PGC-1β gene expression levels in liver were significantly increased during 7 days of fasting and decreased to normal level after refeeding.The expression of PGC-1β was significantly affected by dietary lipid and carbohydrate, significantly higher in liver of fish fed the diet with high carbohydrate and high lipid.The results indicate that PGC-1β is regulated by the energy expenditure status,which implies it plays an important role in energy metabolism in grass carp.