AbstractDietary fiber (DF) has attracted increasing interest from nutritionists. The yield of DF by traditional extraction methods, however, is very low. This paper aims to increase the yield of DF by solid state fermentation using the edible and medicinal fungus Schizophyllum commune. Sweet potato residue (SPR) was selected as raw material for producing DF. Results showed that SPR was a good feedstock for DF production by solid state fermentation. Optimized conditions of solid state fermentation of SPR for DF were obtained as follows: material particle size = 1.8 mm to 2.5 mm, water moisture at 65%, natural lighting radiation, and temperature at 27 °C. Under the optimal conditions, the yield and DF content in fermented SPR were more than 80% and 70%, respectively. The increased DF yield was mainly attributable to increased cellulose and hemicelluloses conversion. Swelling capacity, water-holding capacity, oil-holding capacity, and glucose absorption capacity of the fermented SPR were also determined, and the data indicated that the fermented SPR could be considered as a new good DF. Therefore, this work showed us a novel bioconversion method to produce high-quality DF, and the yield of DF increased 4-fold compared with traditional extraction methods.