Grouper is an important global, marine economic resource. As a low-fat, high-protein edible fish, it is in high demand, and thus, its supply is not adequate to meet this demand. In order to improve the muscle quality of the cultured grouper and provide basic data for the development of compound feed, the nutritional components in the muscles of Epinephelus moara, E. lanceolatus, and E. moara (♀) × E. lanceolatus (♂) (hereinafter Yunlong) were analyzed and evaluated by routine biochemical methods. The results showed that the content of crude protein in the muscles of the three grouper species were 20.60%, 19.30%, and 20.00%, respectively, and the content of crude fat were 2.60%, 1.60%, and 4.30%. Sixteen common amino acids were detected in the muscles of the three grouper species. The content of total amino acids (TAA), essential amino acids (EAA), and delicious amino acids (DAA) in wet-weight fish flesh were respectively 16.95%, 7.11%, and 6.31% in E. moara; 17.46%, 7.18%, and 6.83% in E. lanceolatus; and 18.56%, 7.69%, and 7.16% in Yunlong. The proportions of the essential amino acids in the muscles of three grouper species are all in accordance with the FAO/WHO standard. The ratios of branched chain amino acids to aromatic amino acids (F values) in the muscles of the three grouper species were 2.22, 2.57, and 2.60, respectively. According to the amino acid score (AAS) and chemical score (CS), the first limiting amino acid of the three grouper species was methionine, and the second limiting amino acid was valine. In addition, muscles from the three group species were all rich in minerals. Potassium levels were the highest among those of all macroelements, and zinc levels were the highest among those of all trace elements. Studies have shown that these three species of groupers are high-quality marine fish with high nutritional value, which have good prospects for commercial exploitation and utilization.