Abstract: Wheat bran dietary fiber（WBDF） can adversely affect the quality of flour products while enhancing their nutritional value. In order to improve the quality of flour products rich in WBDF, the effects of different sourdough fermentation methods on the characteristics of WBDF dough and the quality of steamed bread were investigated. The results showed that the internal microstructure of natural fermentation sourdough（LM） was more homogeneous and dense, with lower viscoelasticity, compared with that of the control Lactobacillus plantarum（LP） sourdough fermentation. The specific volume of the steamed bread made from LM increased by 29.28%, mitigating the negative effect of WBDF on the specific volume of the steamed bread. When the addition amount of WBDF was 15%, the fermentation of LM significantly improved the hardness, gumminess and chewiness of steamed bread, which were reduced by 50.12%, 51.87%, and 54.20%, respectively. When the addition amount of WBDF was 15%, the total phenol content, DPPH radical scavenging capacity, and ABTS radical scavenging capacity of LM fermented steamed bread increased by 1.61 mg/g, 5.82 and 9.07 percentage points, respectively. According to the sensory evaluation results, LM fermentation is well accepted in color, appearance, taste, and flavor, which has a positive effect on the sensory quality of WBDF steamed bread. This finding provides an important reference for further improving product quality. In conclusion, sourdough fermentation can effectively improve the specific volume and texture of WBDF steamed bread and enhance their antioxidant capacity, and the overall effect of the steamed bread fermented by LM is better. In this study, innovative solutions were proposed to address the key problems of WBDF steamed bread in terms of roughness and dry and hard texture, and theoretical support was provided to enhance the rheological properties of high-fiber dough and the textural quality of the steamed bread.