The objective evaluation of the quality of the Wuyi rock tea remains challenging. In this study, 649 samples comprising four grades of Wuyi Shuixian tea from the "Spring Tea Competition, 2019" were collected to determine their quality indexes. The results showed that the higher the grade of the Wuyi Shuixian tea, the higher the individual scores from the sensory evaluation. The water extracts, catechin, aspartic acid, and tyrosine were significantly different among the different tea grades. Restricted principal coordinate analysis showed that different grades of Wuyi Shuixian tea could be effectively differentiated using the tea quality indexes and 15 free amino acids. The total quality score of the sensory evaluation was significantly negatively correlated with the hydrophobic amino acids, bitter amino acids, and ECG, and was significantly positively correlated with GCG. These results suggest that the high content of the multicomponents is the material basis of the high quality of the tea. The hydrophobic amino acids, bitter amino acids, ECG, and GCG can be used to evaluate the differences in grades of the Wuyi Shuixian tea. The results of this study are expected to provide a theoretical basis for objectively evaluating the differences in the qualities of the Wuyi Shuixian tea.

Wuyi Rock tea is one of well-known tea in China. The 'Spring Tea Competition' every year is a big event in tea industry of Wuyishan City. In this paper, 667 samples with four grades of Wuyi Rougui teas from 'Spring Tea Competition, 2019' were collected to determine quality indexes. The relationship between the quality index and tea grades was analyzed. The results showed that the higher the grade of teas, the higher the total quality score (TQS) of sensory evaluation. Most of tea quality indexes had the same tendency with TQS. The contents of tea polyphenols, soluble sugar, and catechins were significantly different between the different grades teas. PCoA showed that grades of teas could be effectively distinguished by the tea quality indexes. The contents of tea polyphenols, caffeine, epigallocatechin gallate, and epigallocatechin were significantly and positively correlated to TQS of sensory evaluation. These results suggested that higher content of multicomponents is the material basis of high quality tea. The tea polyphenols, caffeine and catechin can be used to evaluate the grade difference of Wuyi Rougui tea. The ratio of phenols to amino acids, ester catechins to non-ester catechins, and characteristic amino acids are important hallmark of the top tea.