Objective To explore the quality change trend of walnut green husk juice during the concentration process.Methods This paper optimizes the concentration process by the single factor combined with response surface tests, and investigates the effects of temperature, time and rotation speed on the mass fractions of polyphenols and polysaccharides. The antioxidant activity of walnut green husk concentrate is detected, and polyphenols in walnut green husk juice are identified and quantitatively analyzed by adopting high performance liquid chromatography (HPLC).Results The optimal concentration process of walnut green husk juice is the time of 32 min, temperature of 60 ℃, and rotation speed of 41 r/min. In these conditions, the mass fractions of polyphenols and polysaccharides are 59.78 and 39.64 mg/g respectively. In vitro antioxidant tests show that the antioxidant activity of walnut green husk concentrate is stronger than that of walnut green husk liquid, with DPPH free radical scavenging ability (IC₅₀ value of 0.012 mg/g), ABTS free radical scavenging ability (IC₅₀ value of 0.13 mg/g), and hydroxyl free radical scavenging ability (IC₅₀ value of 0.17 mg/g). Additionally, a total of six phenolic substances are detected in the walnut green husk liquid and concentrate, among which the mass concentrations of chlorogenic acid and hydroxybenzoic acid are higher. The mass concentrations of walnut green husk juice are 35.38 and 21.04 mg/L respectively, and those of concentrate are 63.13 and 36.57 mg/L respectively. The mass concentrations of the two phenolic substances are significantly increased after the concentration of walnut green husk juice.Conclusion The walnut green husk concentrate obtained by the optimized concentration process has not only a significant increase in the mass concentrations of polyphenols and polysaccharides, but also stronger antioxidant activity, with the significantly increased mass concentration of main phenolic substances.