Abstract: Soluble dietary fiber(SDF)was prepared by solid fermentation of wheat bran by Neurospora sitophila. The effect of water content,inoculation amount,fermentation temperature and time on SDF yield of wheat bran were studied by the single factor combined with response surface method and the optimum fermentation conditions were obtained. Meanwhile,the activities of cellulase and xylanase in the fermentation process were determined,and the physical and chemical properties of wheat bran SDF were studied. The results showed that the optimum fermentation temperature was 29 ℃,the optimum inoculation amount was 11%(v/w),the optimum water content was 74%(v/w),the optimum fermentation time was 83.5 h and 13.41% SDF was extracted,which was 1.05 times higher than that of un-fermented wheat bran. The activities of cellulase and xylanase were positively correlated with the yield of SDF during the fermentation process. After fermentation,solubility,glucose adsorption ability,cholesterol adsorption ability(pH=2 and pH=7)and DPPH scavenging ability of wheat bran SDF were increased by 1.14,1.76,5.36,4.61 and 1.62 times respectively. These results provided a theoretical basis for wheat bran SDF as a food additive.