The taste of tea infusions is one of the important factors to evaluate the quality and classify the grade of tea. In order to explore the key components that cause the difference in different grades of Dianhong tea infusions， this study systematically studied the taste quality of different grades of Dianhong tea infusions by combining sensory evaluation， electronic tongue and ultra-performance liquid chromatography-quadrupole orbital trap mass spectrometry. The results showed that the taste attributes of 12 Dianhong infusions were divided into three groups (superior-quality group， good-quality group and poor-quality group) according to the sensory evaluation. The results of electronic tongue were consistent with the sensory evaluation. The response of electronic tongue sensors corresponding to different taste properties to the three groups of tea infusion was different. Further， the metabolomics were studied by ultra-performance liquid chromatography-quadrupole orbital trap mass spectrometry. A total of 116 compounds were detected， including 26 amino acids and their derivatives， 15 catechins and their polymers， 16 phenolic acids， 15 nucleotides and their derivatives， 20 flavonoids (alcohols) and their glycosides， 6 alkaloids， 11 organic acids， 2 sugars and 5 other classes. In addition， three groups of Dianhong tea infusions were well distinguished by using orthogonal partial least squares regression analysis (R2Y=0.985， Q2=0.902). In addition， based on VIP>1.2 and significance P<0.05， a total of 7 key differential components affecting different grades of tea infusions were screened out， specifically， arginine， gallatechin， epicatechin， uric acid， abscisic acid， niacin， adenosine-5 '-diphosphate. The results provided theoretical support for quality evaluation and quality control of different grades of Dianhong tea infusions.