To investigate the taste characteristics and key taste components of different categories and different grades within the same category of Wuyi black tea, four categories of Wuyi black tea, namely 'Qihong' (Jinjunmei), 'Zhengshan xiaozhong', 'Xiaozhong', and 'Yanxiaozhong' (with a total of 12 graded samples) were used as materials. Sensory evaluation was adopted to analyze the taste characteristics, while high-performance liquid chromatography (HPLC) and ultra-high performance liquid chromatography-quadrupole-time-of-flight tandem mass spectrometry(UHPLC-Q-TOF/MS) were used for the qualitative and quantitative analysis of non-volatile components. Multivariate statistical analysis was applied to screen for differential metabolites. The results showed that the taste differences among the four categories of Wuyi black tea are mainly derived from the differences in the types and contents of tea polyphenols and their derivatives, organic acids, amino acids and their derivatives, and nucleotide compounds. The water extract content (34.47%-41.50%), total free amino acids (2.83%-4.98%), total catechin components (1.96%-2.66%), and tea polyphenols content (11.79%-21.50%) of 'Qihong' are significantly higher than those of the other categories, and the synergistic effect of multiple components contributed to its sweet, mellow and smooth taste. The characteristic taste of 'Zhengshan xiaozhong' is dominated by a dried longan flavor, with flavonoids (such as eriodictyol and isoquercitrin) and amino acidic compounds being the core contributing substances. The taste of 'Xiaozhong' and 'Yanxiaozhong' is significantly influenced by acidic compounds, and 'Yanxiaozhong' has a unique smoky flavor. Differential metabolites among different grades within the same category are species-specific: those of 'Qihong' are dominated by organic acids, nucleotides, and catechins; those of 'Zhengshan xiaozhong' are characterized by flavonoids and amino acids as core differential components; those of 'Xiaozhong' are primarily composed of amino acids and flavonoids; while those of 'Yanxiaozhong' are mainly nucleotides and amino acids. These components directly regulate the taste intensity and characteristic expression of products at different grades.