Abstract: A strain of Asperillus niger which could produce citric acid with cellulose materials was isolated from the soil by screen. The results of study showed that the suitable cellulose material on the strain was pretreated rice straw. The characteristics indicated that it secreted cellucase were that the CMCase activity reached218.4U/mL, the FPase activity to 44.1U/mL, with 3% pretreated rice straw, at 12 h, and then decreased. The acid production rate reached 22% at 60 h. The strain Asperillus niger S6 which could produce citric acid stably was obtained by domesticated screening and rescreening. Asperillus niger S6 could be the strain of citric aicd-producing with cellulose materials.