Abstract: Taking tea residue as the raw material, soluble dietary fiber (SDF) was prepared by mixed strain of Lactobacillus bulgaricus and Streptococcus thermophilus fermentation (1∶1) . Effect of inoculating volume, fermentation temperature, fermentation time and ratios of material and liquid on yield of SDF were investigated, the fermentation conditions were optimized by single-factor experiments and orthogonal test. The result showed that the optimum condition of extracting SDF was as follows:inoculating volume 3%, fermentation temperature 40℃, fermentation time 25h, ratio of material and liquid by 1∶10. Under these conditions, the average SDF yield was 10.99%.