In order to investigate the influence of highland barley on the fermentation flavor and functional components of Monascus vinegar， the changes in physicochemical indicators and microorganisms during the fermentation process of highland barley Monascus vinegar with 0% (control)， 20%， and 40% highland barley were comparatively investigated. The flavor characteristics and major functional components of highland barley Monascus vinegar aged for 90 days were measured using liquid chromatography-mass spectrometry-based metabolomics techniques. The results showed that the addition of 20% and 40% highland barley had no significant effect on physicochemical changes such as reducing sugars， alcohol content， acidity， amino acid nitrogen， and color intensity during the 30-day fermentation of highland barley Monascus vinegar， as well as the microbial growth， such as yeast， lactic acid bacteria， and acetic acid bacteria. The content of total organic acids， acetic acid and succinic acid， flavonoids， polyphenols， and monacolin K， in highland barley Monascus vinegar was significantly higher than that in the control group aged for 90 days (P<0.05). Moreover， the DPPH and ABTS free radical scavenging capacities of 20% highland barley Monascus vinegar were 25.05% and 45.39% higher than those of the control group， indicating its strong antioxidant activity. Furthermore， metabolomics analysis identified 353 differential compounds between 20% highland barley Monascus vinegar and the control group， including 8 organic acids， 6 amino acids， 2 lipids， and 5 phenolic compounds. Thus， the addition of 20% highland barley did not affect the physicochemical and flavor quality of Monascus vinegar during fermentation and aging， but significantly increaseed the content of functional active components such as organic acids and phenolic acids， as well as antioxidant activity. This provided a theoretical basis for further functional research on highland barley Monascus vinegar.