The tomato hind, Cephalopholis sonnerati, a high-value marine species endemic to the South China Sea, is renowned for its economic importance and market potential. Despite its importance, research on this species has primarily focused on its spawning behavior, reproductive patterns, and genome assembly. This study systematically investigated the gonadal development and muscle nutritional composition of C. sonnerati across its gonadal development stages, aiming to elucidate its biological characteristics and nutritional value, thereby supporting its aquaculture development. Histological observations of C. sonnerati gonads revealed distinct gonadal development patterns. During the first three months, gonadal development progressed slowly. Four months onward, the development rate increased significantly from 4 to 13 months of age. The gonadal somatic index remained stable during this process but showed a significant increase in broodstock at the mature gonadal stage (stage Ⅴ). Mature gonads exhibited a high degree of development, which supports robust reproductive capability. These findings established a clear timeline for the reproductive maturation of C. sonnerati and underscored the importance of tailored aquaculture practices during these critical stages. To further understand the implications of gonadal development on nutritional status, this study analyzed muscle composition across five gonadal development stages (Ⅰ–Ⅴ). Key parameters such as water, protein, and lipid content were evaluated. The results revealed that water and protein content continuously increased from stages Ⅰ to Ⅰ. Lipid content peaked during stage Ⅳ but declined significantly at stage Ⅴ. This pattern indicates heightened metabolic activity during the reproductive phase, when lipids are mobilized to support gonadal development. As primary energy sources, lipids and proteins play a crucial role in sustaining cell growth and reproductive maturation. At stage Ⅴ, C. sonnerati achieved its maximum crude protein content (21.27±0.21 g), a value notably higher than that of most other marine fish species (commonly 13.90–21.03 g) and reported groupers. These findings highlight C. sonnerati as a premium high-protein marine fish with significant implications for its commercial value. The total amino acid (TAA) content in C. sonnerati muscle ranged from (18.20±0.26)% to (19.63±0.06)%, encompassing all seven essential amino acids (EAAs) required for human health. The EAA index of C. sonnerati exceeded that of most other economically significant fish species. The ratio of EAAs to TAAs ranged from (39.34±0.34)% to (40.49±0.24)%, closely aligning with the FAO/WHO ideal value of 40%. Similarly, the ratio of EAAs to non-EAAs ranged from (75.98±0.74)% to (80.33±0.85)%, significantly higher than the FAO/WHO recommended standard of 60%. Compared to stages Ⅰ to Ⅳ, nutritional quality peaked in the muscle of stage Ⅴ broodstock. Furthermore, C. sonnerati contained six flavor-related amino acids, with their total content ranging from (8.76±0.10)% to (9.24±0.08)%, surpassing levels found in other grouper species. This indicated that C. sonnerati not only possessed high nutritional value but also offered superior taste quality. Using amino acid and chemical scores, methionine and cysteine were identified as the first limiting amino acids in C. sonnerati, whereas valine was identified as the second limiting amino acid. These findings suggest that the supplementation of aquaculture feed formulations with these amino acids can significantly enhance the growth and reproductive performance of C. sonnerati. In addition to amino acids, 25 fatty acids have been identified in the muscle tissues of C. sonnerati. Palmitic acid (C16:0) and oleic acid (C18:1) were the most abundant but showed a declining trend during gonadal development, indicating their mobilization and transfer to support oocyte maturation and reproductive energy metabolism. Conversely, docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) levels peaked during stage Ⅴ, exceeding those reported in most marine fish species. This highlighted their pivotal role in energy supply during reproduction and their potential health benefits for human consumption. Mineral composition analysis revealed that C. sonnerati muscle contained five major macro elements: phosphorus, magnesium, potassium, sodium, and calcium. Among the trace elements, zinc and selenium were found in significant quantities across all developmental stages. Selenium content, which was particularly high in stage Ⅴ broodstock, was superior to that in other groupers. Selenium plays a vital role in enhancing immune function, preventing cardiovascular diseases, and improving antioxidant activity. The combination of high levels of selenium and other abundant minerals such as phosphorus and magnesium positioned C. sonnerati as an excellent dietary source of essential nutrients. A comprehensive nutritional evaluation of C. sonnerati underscored its value as a high-quality marine fish species. Rich in EAAs, fatty acids, and minerals, C. sonnerati demonstrated exceptional nutritional and health-promoting properties. Its superior protein content, coupled with the abundance of DHA, EPA, and selenium, makes it particularly suitable for human consumption and a promising candidate for aquaculture promotion. The findings of this study not only emphasize the dietary and economic potential of C. sonnerati but also provide critical insights for optimizing aquaculture practices. By understanding nutrient mobilization patterns during gonadal development, aquaculture practitioners can develop stage-specific feeding strategies to enhance growth, reproductive performance, and overall fish quality. Furthermore, the identification of limiting amino acids suggests opportunities to improve feed formulations to support optimal development. In conclusion, C. sonnerati is a highly nutritious and economically valuable species with immense potential for sustainable aquaculture. Its rich nutritional profile, superior muscle quality, and protein content make it a promising seafood product. The results of this study serve as a valuable reference for the formulation of efficient aquaculture feeds tailored to the different developmental stages of C. sonnerati, contributing to the broader goal of advancing sustainable marine aquaculture.