Taste serves as the foundation for choosing food and is one of the most vital senses of animals. Numerous taste cells, specialized structures that can sense taste, form taste buds. Taste receptors are present in the membranes of these cells. Taste receptors include type I and type II receptors, which are responsible for identifying distinct flavors in food. The taste receptor type I (T1R) family plays a crucial role in the identification of nutrients in the environment. TIR family genes rely on different heterodimers for flavor recognition and can recognize fresh (T1R1+T1R3) and sweet (T1R2+T1R3) flavors. Animal feeding habits are frequently associated with the number and replication of T1R family genes. Mandarin fish (Siniperca chuatsi) have a unique carnivorous lifestyle and eat live bait throughout their lifetimes. To understand the correlation between the quantity and expression patterns of T1R family members in mandarin fish and their carnivorous nature, gene family analysis was conducted to identify T1R family member genes in mandarin fish genomic data. Changes in the T1R family member gene expression levels were then determined using Quantitative Real-time PCR (qPCR) from to 0–30 days post hatching (0–30 dph) and after the domestication of their diet. This study found that the T1R family in mandarin fish comprises four genes, t1r1, t1r2a1, t1r2a2, and t1r3, each of which possesses complete sequences and structural domains. The t1r2 gene was duplicated as t1r2a1 and t1r2a2, and the exons of both displayed identical structural domains. However, the length of the 3rd, 4th, and 5th introns and 5' UTR varied among them. Selection pressure (dN/dS) analysis indicated positive selection for t1r1 in mandarin fish, whereas t1r2s and t1r3 showed negative selection. The possible cause of evolutionary pressure on the umami receptor gene t1r1 might be related to the uncommon diet of this fish species. The expression of four taste receptor type I genes, t1r1, t1r2a1, t1r2a2, and t1r3, began before the oropharyngeal cavity of mandarin fish was completely formed, and increased after 20 d. The umami receptor gene (t1r1) was found to have a much higher expression among these genes than that of the sweet taste receptor gene (t1r2s). All four t1r genes showed lower expression levels after domestication, with t1r1, the umami receptor gene, showed the most significant downregulation. These findings provide fundamental data for investigating the effects of taste receptor genes on the development and adaptation of mandarin fish to carnivores.