Abstract: To develop probiotic fermented new products and realize the value-added utilization of pitaya peel, the antioxidant ability of pitaya peel beverage fermented by Lactobacillus plantarum was investigated by means of different free radicals antioxidant experiments in vitro, and the content of pigment, polysaccharide, total flavonoid of unfermented and fermented were analyzed.The results showed that the pitaya peel beverage both unfermented and fermented had a strong scavenging ability to superoxide anion ( O₂^-·) , DPPH free radicals, and a certain scavenging ability to hydroxyl free radical (·OH) , nitrite ion ( NO₂^-) , within a certain range, the clearance rate increased with the increase of sample concentration.The IC₅₀ of fermented pitaya peel beverage to hydroxyl free radical (·OH) , superoxide anion ( O₂^-·) , nitrite ion ( NO₂^-) and DPPH free radicals respectively were 0.77, 0.33, 0.47, 0.17 m L/m L, which decreased by 25.96%, 28.26%, 47.78%, 57.50% respectively compared with unfermented.Fermentation could effectively improved the free radical scavenging capacity of pitaya peel beverage at the same concentration, but the increase amplitude decreased gradually with the increase of concentration, pigment and total flavonoid concentration decreased after fermentation, but the content of polysaccharide increased.This suggested that fermented by Lactobacillus plantarum could further improve the antioxidant capacity of pitaya peel, provided theoretical basis for the development of pitaya peel hygienical and probiotic fermented products.