The glucose-6-phosphatase catalytic subunit (G6PC) is an important component of the glucose-6-phosphatase (G6Pase) system, which controls glucose production from glycogenolysis and gluconeogenesis, and plays a key role in blood glucose homeostasis. G6pc can catalyze the hydrolysis of glucose-6-phosphate to glucose and inorganic phosphate in the living body. Despite its importance, little is known about the function of different ). We obtained three gene sequences from the grass carp genome using homologous sequence alignment, which were named through sequence alignment and a phylogenetic tree. Deduced amino acid sequences of cDNA sequences in grass carp shared similarities of 85%-94%, 64%-83%, and 54%-66% with zebrafish (Homo sapiens), respectively. In addition, synteny analyses of were identical with that of zebrafish. This indicates that g6pc mRNA expression was detected in different tissues. The results showed that the mRNA expression level of was highest in the brain, followed by the liver and adipose tissue. Expression of was most strongly observed in the liver, and weakly observed in the midgut and kidney. The mRNA level was highest in the heart, followed by adipose tissue. To explore the role of different g6pc mRNA levels in carps with different diets with normal or high level of carbohydrates. The results revealed that a high carbohydrate diet significantly increased the mRNA expression level of g6pcb2 mRNA levels. Compared with the control group, 15 mmol/L glucose obviously increased the expression of mRNA in L8824, while 30 mmol/L glucose had no remarkable influence, and insulin at a concentration of 1 mmol/L could overcome the stimulatory effect of 15 mmol/L glucose. Our results suggest that the genes of grass carp might have functional differentiation after gene duplication events. In addition, high glucose levels induced the expression of g6pcb1 and , the specific functions of which require further study.