The hydrogen peroxide decolorization process of polysaccharide extracted from red dragon fruit peel was investigated in this study. The effects of the hydrogen peroxide concentration, the decolorization temperature and the decolorization time on the decolorization rate were studied. The optimum conditions were obtained by response surface methodology. Moreover, the antibacterial activity of the polysaccharide was also investigated. The results showed that the optimum hydrogen peroxide decolorization conditions were the hydrogen peroxide concentration of 4.3%, decolorized at 62 ℃ for 109 min. Under these conditions, the decoloriza-tion rate and the retention rate of the red dragon fruit peel polysaccharide were 88.17% and 82.39%, respectively. The polysaccharide exhibited significant inhibitory effects on Escherichia coli, Bacillus cereus, Bacillus subtilis, and Staphylococcus aureus.