The improved strain (HR-5) of Pyropia haitanensis was characterized by thin blade, good taste, fast growing and high production of conchospores. In order to develop it into a new variety, the contents of crude protein, total amino acid and free amino acid of HR-5 strain and the native cultivated strain (WT-dt) of P. haitanensis cultivated in mariculture farm were determined in this study. The results showed that, ① The contents of crude protein from the first three harvests' blades were 45.2%-38.0% in HR-5 strain, and were 39.5%-33.2% in WT-dt strain, the former was significantly higher than the latter in three harvest periods (P<0.05), and with the increase of harvesting time, the contents of crude protein from both strains decreased gradually. ② The contents of total amino acids were 361.8-287.4 mg/g in HR-5 strain, and were 321.8-264.8 mg/g in WT-dt strain, the former was significantly higher than the latter in three harvest periods (P<0.05), and with the increase of harvesting time, the contents of total amino acids and essential amino acids from both strains decreased gradually. ③ The contents of free amino acids were 3 391.8-1 983.2 mg/100 g in HR-5 strain, and were 2 930.2-2 046.7 mg/100 g in WT-dt strain. The contents of free amino acids of HR-5 strain in the first and second harvest periods were significantly higher than those of WT-dt strain (P<0.05). ④ The contents of mainly flavor amino acids of HR-5 strain were significantly higher than those of WT-dt strain in three harvest periods (P<0.05), and with the increase of harvesting time, the contents of free amino acids and flavor amino acids from both strains decreased gradually. The above results confirmed that the contents of crude protein, total amino acid, free amino acid and mainly flavor amino acid of HR-5 strain were higher than those of WT-dt strain, and that’s the reason why the taste of the former were better than that of the latter. This study also provided basic data for developing HR-5 strain into a new variety of P. haitanensis.