Based on the enrichment culture strategy, a novel N-methylmorpholine-N-oxide (NMMO)-tolerant cellulase-producing strain Galactomyces sp. CCZU11-1 was isolated from soil samples. After the optimization of culture condition, the highest FPA (13.4 U/mL) and CMCase (24.5 U/mL) were obtained. In both culture and reaction media containing NMMO 25% (w/v), the cellulase from Galactomyces sp. CCZU11-1 still had good activity. Furthermore, high saccharification rate was obtained in aqueous-NMMO media. Moreover, the fermentability of the hydrolyzates, obtained after enzymatic in situ saccharification of the NMMO-pretreated sugarcane bagasse, was evaluated using Saccharomyce scerevisiae. In conclusion, Galactomyces sp. CCZU11-1 is a promising candidate as high NMMO-tolerant cellulase producer and has potential application in future.