Ultrafiltration and strong anion exchange chromatography were used to isolate and purify the protease hydrolysates of Prinsepia utilis Royle. The free radical scavenging rate of 1,1-diphenyl-2-picrylhydrazyl(DPPH) was used as the evaluation index to screen the peptide components with better antioxidant activity. The peptide sequence was identified by LC-MS/MS, and its physicochemical properties were analyzed by bioinformatics methods, and the secondary structure characteristics and docking sites with Keap1 protein were further analyzed by infrared spectroscopy and molecular docking technology. The results showed that the F-1 fractions had better antioxidant activity among the four component, and its DPPH free radical scavenging rate reached 27.67%. The peptide components with higher activity and molecular weight less than 1 kDa were selected, and the IC₅₀ values of DPPH free radical scavenging of the three peptides (TALDVPPPR, TLSDAGVGGL, and DLINGGKDA) were 0.43,0.83, and 0.51mg/mL, respectively, the antioxidant activity of TALDVPPPR was relatively high. Secondary structure analysis showed that the three antioxidant peptides were composed of α-helix, β-fold and β-turn, and the content of α-helix in TALDVPPPR was relatively low, making it easier to bind to free radicals. Molecular docking results showed that TALDVPPPR, TLSDAGVGGL and DLINGGKDA bound to Keap1 protein by hydrogen bond and hydrophobic interaction, and released Nrf2 into the nucleus to activate the expression of a series of proteins with antioxidant and cell protective effects, that is, activate the Keap1-Nrf2/ARE pathway to play an antioxidant role. Therefore, TALDVPPPR, TLSDAGVGGL and DLINGGKDA could be used as new antioxidants. The purpose of this study was to provide theoretical reference for the development and utilization of functional peptides from Prinsepia utilis Royle.