Abstract: In this experiment, the black glutionous corncob and Huayu 15 corncob were used as the experimental objects. The raw materials were pretreated with α-amylase, saccharifying enzyme and neutral protease, and the soluble dietary fiber of corncob was prepared by cellulase. In this experiment, the extraction conditions of soluble dietary fiber from black glutionous corncob were optimized by orthogonal experiment. At the same time, the reducing sugar, total phenols, anthocyanin content, thermostability, infrared spectrum and ultrastructure of corncob soluble dietary fiber were determined, and their antioxidant activities were also studied. The results showed that the optimum condition was as follows:the liquid ratio 1:25 g/mL, the content of cellulose enzyme 2.5%, temperature 45℃, enzymolysis time 70 min. Hence, the maximal content of soluble dietary fiber form dry black glutinous corncob was determined, which was 4.36%. Under these conditions, the dietary fiber of black glutionous corncob and corn cob Huayu 15 were extracted and compared with two soluble dietary fiber. Compared with the Huayu 15 corncob, the content of phenol and reducing sugar of the soluble dietary fiber in the black glutinous corncob was higher, the thermal stability was weaker, the structure had a larger surface area and more biological activity. The scavenging ability of DPPH free radical and hydroxyl radical were higher than that of the Huayu 15 corncob, which showed a good antioxidant activity.