Abstract: Effects of carbon and nitrogen sources on the biosynthesis of β- glucosidase by Aspergillus niger nl- 1 were investigated. The results showed that bran was the best carbon source for β - glucosidase production among the studied carbon sources, and its preferable concentration was 4%. In the experimental sources of nitrogen, (NH4)2SO4 and the peptone were the best nitrogen source to produce β -glucosidase as inorganic nitrogen and organic nitrogen, respectively. Moreover, the indueing β - glucosidase ability of mixture nitrogen source was better than that of a single nitrogen source. The favorable ratio of them was 0.2% ammonium sulfate and 3. 19% peptone. In these eases, the highest activity of β - glucosidase, 4.82 U/mL, was obtained.