Abstract: The antioxidant activity of day lily juice before and after enzymatic digestion was investigated by the optimization of the enzymatic digestion process using day lily as raw material. In this study, the enzymatic hydrolysis experiments with different ratios of cellulase and pectinase were carried out, and the best enzymatic digestion process of day lily juice was determined by response surface optimization using the juice yield of day lily as an index. The polyphenols in the samples were analyzed qualitatively and quantitatively by high performance liquid chromatography-triple quadrupole mass spectrometry, and the antioxidant activity of the samples in vitro was also evaluated. The optimal enzymolysis conditions were obtained as follows: Enzymatic digestion temperature at 50 ℃ and time of 2 h, the total enzyme addition of 0.4% per 100 g of day lily juice (1:1 ratio of day lily to water), and cellulase:pectinase=1:3 , and the juice yield was 78.54%. The total phenol content increased by 1.3 times, the DPPH free radical scavenging rate increased by 9.02%, and the ABTS⁺ free radical scavenging rate increased by 6.15%. The correlation coefficient between total phenol and DPPH free radical scavenging capacity was 0.929, and the correlation coefficient between total phenol and ABTS⁺ free radical scavenging capacity was 0.968, indicating that the antioxidant capacity in vitro of day lily juice was closely related to the change of total phenol content.