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 WBDF-enriched flour products, this study investigated the effects of different sourdough fermentation methods on WBDF-dough characteristics and steamed bread quality. 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 (Saccharomyces cerevisiae fermentation) and Lactobacillus plantarum (LP) sourdough fermentation; and the specific volume of the steamed bread made by LM was elevated by 29.28%, which mitigated the negative effect of WBDF on the specific volume of the steamed bread. When WBDF was added at 15%, LM fermentation significantly improved the hardness, chewiness, and gelatinization of steamed bread by 50.12%, 51.87%, and 54.20%, respectively. As for antioxidant activity, the total phenol content, DPPH radical scavenging capacity, and ABTS radical scavenging capacity of LM fermented steamed bread increased by 1.61 mg/g, 13.89%, and 9.07%, respectively, when WBDF was added at 15%. Through the sensory evaluation results, it can be seen that LM fermentation has a good acceptance 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, it can be seen that sourdough fermentation can effectively improve the specific volume and texture of WBDF steamed bread, enhance the antioxidant capacity, and the overall effect of LM-fermented steamed bread 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.