Abstract: CCK as brain-gut peptide, binds to its receptor (CCKR) and participates in physiological processes such as feeding and digestion in animals. In order to study the function of CCKs and CCKRs in largemouth bass (Micropterus salmoides) in feeding activities, the coding sequences of CCK1, CCK2, CCK1R and CCK2R were cloned in this study. Their lengths were 414, 387, 1368 and 1359 bp, and their encodes were 137, 128, 455 and 452 amino acids, respectively. Fluorescence quantitative results showed that both CCK1 and CCK2 were highly expressed in brain, followed by intestinal, while CCK1R and CCK2R were highly expressed in gallbladder and brain, respectively. Within 24h after ingestion, the relative expressions of CCK1, CCK2, CCK1R and CCK2R increased first and then decreased. The relative expression of CCK1, CCK1R and CCK2R reached the highest value at 3h after ingestion, while the relative expression of CCK2 was at 12h after ingestion. The relative expression reached the highest value (P<0.05). During fasting, the relative expression ofCCK1, CCK1R and CCK2R was significantly increased on the 14th day of fasting (P<0.05). The relative expression trends ofCCK1, CCK1R and CCK2R after refeeding were similar to those after meals, showing a trend of first increasing and then decreasing. However, there was no significant change in the relative expression of CCK2 during fasting and refeeding. In conclusion, the results of this study indicated that CCK1 can be combined with CCK1R and CCK2R to act as a satiety signal factor to regulate physiological processes such as feeding and digestion of largemouth bass by suppressing appetite; CCK2 may act as a short-term appetite factor to regulate feeding. Activity. The results of this study can provide a theoretical basis for the regulation of feeding activities of largemouth bass.