The production of cellulase from Aspergillus glaucus HGZ-2 was improved by using genome shuffling. The starting populations, obtained by UV irradiation, were subjected to recursive protoplast fusion. The optimal conditions for protoplast formation and regeneration were 7 mg/ml snailase and 5 mg/ml cellulase at 34 A degrees C for 3.0 h using 0.7 M NaCl as an osmotic stabilizer. The protoplasts were inactivated under UV for 30 min or heated at 50 A degrees C for 50 min, and a fusant probability of about 100 % was observed. The positive colonies were created by fusing the inactivated protoplasts. The optimal conditions for protoplast fusion were PEG6000 concentration of 35 %, CaCl2 concentration of 0.02 M, and incubation time of 12 min. After two rounds of genome shuffling, one strain (Y) was obtained. Its filter paper cellulase (FPase) and carboxymethyl cellulase (CMCase) activity reached 71 and 70 U/ml, respectively, which were increased by 1.95-fold and 1.72-fold in comparison with that of its ancestor strain. The results indicated that genome shuffling was an efficient means for the improved production of cellulases by A. glaucus HGZ-2.