A preparation method for a xylooligosaccharide powder rich in dietary fibers comprises the following steps: carrying out pretreatment, cooking treatment, pulp washing treatment, first enzymolysis treatment and separation and cleaning treatment of a bamboo raw material successively, to obtain a sugar liquid and a fiber residue; carrying out refined purification and concentration treatment of the sugar liquid, to obtain a refined sugar liquid; carrying out secondary enzymolysis treatment, rinsing treatment and drying treatment of the fiber residue successively, to obtain a dried fiber, wherein the water content of the dried fiber is controlled at 0.5%-20%; mixing the refined sugar liquid and the dried fiber, to obtain a mixed slurry, wherein the mixing ratio of the refined sugar liquid to the dried fiber is (100-1):(30-80); and carrying out drying treatment of the mixed slurry to obtain the xylooligosaccharide powder. The prepared xylooligosaccharide powder rich in the dietary fibers canrelieve the characteristic of moisture absorption of xylooligosaccharide, and is convenient to use.