Objective To improve the polyphenol utilization and antioxidant activity of black highland barley.Methods Black highland barley was treated using ultrasonic treatment (UT), microwave treatment (MT), and ultraviolet irradiation treatment (UVT). The differences in basic nutritional components, phenolic content, phenolic composition, and antioxidant activity were comparatively analyzed.Results Compared with the untreated group, the fat content of black highland barley significantly increased (P<0.05) after all three treatments, while the fiber content significantly decreased (P<0.05). The total phenolic and total flavonoid content were significantly increased (P<0.05) by all three treatments, reaching 1.03~1.19 times and 1.24~1.46 times those of the untreated group, respectively. Among them, UT significantly enhanced polyphenol content in black highland barley, increasing total phenolics and total flavonoids by 18.72% and 46.22%, respectively. UVT mainly increased hydroxycinnamic acids and flavonols, UT primarily increased flavonoids and flavanols, while MT mainly increased hydroxybenzoic acids. The antioxidant potency composite index (APC) of black highland barley treated by the three methods ranked as follows: UT (99.94%)>UVT (93.35%)>MT (82.91%)>CK (74.10%). There was a strong correlation between phenolic compounds and antioxidant activity.Conclusion UT resulted in the highest phenolic content and antioxidant activity in black highland barley.