ACEI and Xyr1 are two regulators that potentially involve in regulation of cellulases and xylanases formation in Trichoderma reesei, they compete for a binding site in the xyn1 (Xylanase1-encoding) gene promoter. To further investigate the mechanism for the transcriptional regulation of cellulases, DNA-binding domains of both ACEI and Xyr1 in T. Koningii were expressed from E. coli. They both showed bindings to the cbh1 promoter fragment (-304 bp to -18 bp) by electrophoresis mobility shift assays, suggesting ACEI and Xyr1 not only compete for binding to xyn1 promoter but also to cbh1 promoter.