The strain Penicillium purpurogenum P-26 was subjected to UV irradiation and N-methyl-N’-nitro-N-nitrsoguanidine treatment and mutants were isolated capable of synthesizing cellulase under the conditions of a high concentration of glucose, Initially mutants resistant to catabolite repression by 2-deoxy-D-glucose were isolated on Walseth’s cellulose/agar plates containing 15-45 mM 2-deoxy-D-glucose. These mutants were again screened for resistance to clatabolite repression by glycerol or glucose on Walseth’s cellulose/agar plates containing 50 g/l glycerol or 50 g/l glucose respectively. Four mutants with different sizes of clearing zone on Walseth’s cellulose/agar plates containing 50 g/l glucose were selected for flask culture. Among them, the mutant NTUV-45-4 showed better carboxymethylcellulase activity in flask culture containing 1% Avicel plus 3% glucose than did the parental strain.