Pectin-derived oligosaccharides, an important source of the new generation of prebiotics, have aroused widespread research. As per our previous study report, the rhamnogalacturonan-I (RG-I) type pectin of dragon fruit positively affects the proliferation of Bifidobacterium animalis subsp. Lactis 3296. However, the pectin region that primarily produces prebiotic effects is not clear. To further investigate the promotion of the dragon fruit pectin RG-I domain on the proliferation of B. animalis subsp. Lactis 3296, we first obtained pectin (DP-AC-A2a) with a higher proportion of the RG-I region through gel purification and enzyme digestion. Then, monosaccharide components and Fourier transform infrared were analyzed to identify the pectin structures preliminarily. The results demonstrated that DP-AC-A2a with a backbone consisting of repeated →