Abstract: In order to evaluate the effect of ultrafine grinding on the physical properties and antioxidant activities of black garlic powder, the physicochemical properties, such as the angle of repose, loose density and water holding capacity of black garlic powder, were analyzed. Moreover, the extraction yield of polyphenols was determined. Simultaneously, the antioxidant assays such as 2, 2'-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging ability, Fe³⁺ reduction assay, 2, 2-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) scavenging activity, oxygen radical absorbance capacity (ORAC) were used to evaluate the antioxidant properties under the different treatment. Furthermore, HepG2 cells were used as the model to determine cellular antioxidant activity (CAA).The results showed that the average particle size of the black garlic powder was relatively small. Moreover, the water soluble, degree of swelling and extraction rates of phenolics was increased under superfine grinding treatment by 26.84%, 39.53% and 31.76%, respectively.The physicochemical properties such as water holding capacity and oil holding capacity of black garlic samples was improved. It indicated that superfine ground can significantly improve the reducing ability, DPPH and ABTS⁺ free radical scavenging ability, ORAC and intracellular antioxidant activitiesof black garlic.