Abstract: In order to explore the distribution of pentosan in different system flours produced in the wheat milling process and the effect of different content of pentosane on the quality of steamed bread, 48 kinds of system flour were taken from in a wheat milling workshop as the research object. The content of pentosan was determined by the resorcinol-glacial acetic acid method, and different amounts of pentosan were added to wheat flour for steamed bread steaming experiments. The results showed that the content of pentosan in wheat system flour was 0.25%-3.01%, which was mainly concentrated in the rear flour of M, D and B. With the increase of pentosan addition, the specific volume of steamed bread increased first and then decreased, while the aspect ratio showed the opposite trend. The L^* value inside and outside of the steamed bread increased and then decreased, the a^* value gradually increased, and the b^* value decreased. The hard of the steamed bread first decreased and then increased, the cohesiveness decreased, the chewiness increased significantly, and the springiness and resilience did not change significantly. The scores of the steamed bread′s specific volume, elasticity, surface color, surface structure and internal structure, and total score all increased and then decreased. The viscosity and taste scores gradually decreased, the toughness increased, and the aspect ratio did not change significantly. When the content of pentosan was 1.0%, the steamed bread scored the highest at 79.8 points. In each system flour, the content of pentosan increased from front to back, from top to middle and then to bottom, and the content was highest in 8M flour; the addition of 0.5%-1.0% pentosan could significantly improve the volume, color, texture, and sensory characteristics of the steamed bread, but excessive pentosans could deteriorate the qualities of the steamed bread.