The present study aimed to explore the relationship between the grade and the characteristic aroma in Keemun black tea (KBT). Headspace solid-phase microextraction (HS-SPME), gas chromatography-mass spectrometry (GC-MS), sensory evaluation, and chemometrics were employed to determine the changes in the flavor evolution of KBT at grade. The results showed that a total of 110 volatile components were identified. Linalool and linalool oxide were dominant. The orthogonal partial least squares discriminant analysis (OPLS-DA) combined with relative odor activity value (rOAV > 0.1) revealed that 11 volatile components were the key volatile compounds of KBT, such as benzeneacetaldehyde (rOAV: 3.43-5.96) and methyl salicylate (rOAV: 2.15 - 2.50). Furthermore, the partial least squares (PLS) model indicated that geraniol, linalool, and methyl salicylate benefited from the reservation of floral flavor of Keemun aroma characteristic of KBT. The findings presented in this thesis add to our understanding of KBT at different grades.