In this study, furfural residues were used as a substrate for cellulase production by the fungi Trichoderma reesei. The results indicated that a low pH and the presence of lignin in the furfural residues have an obvious impact on cellulase production by T. reesei. After pH adjustment, furfural residues could be used for cellulase production by T. reesei, with a higher filter paper activity (FPA) and a higher activity of CMCase compared to that yielded from furfural residues with pH unadjusted. After being washed with 1.6% (w/v) H₂O₂, all of the lignin in the furfural residues was removed, and an FPA of 7.1 FPU ml⁻¹ and a CMCase activity of 3.4 IU ml⁻¹ were obtained in 115 h, while pretreated straw could yield an FPA of 8.0 FPU ml⁻¹ and a CMCase activity of 2.7 IU ml⁻¹ in 160 h. Moreover, after being treated with H₂O₂, furfural residues could be used as an inducer in the production of cellulases. With the treated furfural residues added into the medium at the beginning of cultivation, T. reesei gave the maximum FPA (8.4 FPU ml⁻¹) and CMCase activity (4.8 IU ml⁻¹) at 142 h from pretreated straw, which is relatively high for cellulase production compared to that from most other agricultural wastes reported.