[Objective] The aim was to select effective method to breed high-yield strains of cellulase.[Method] Using Aspergillus niger as starting strain,the mutant with high enzyme activity were bred after compound mutation of ultraviolet and nitrite mutation for the further culture,and then its enzyme activity was detected.[Result] The effect of ultraviolet was obvious better than that of nitrite mutation in single factor mutation and the mutagen dosage with 70%-80% lethality was more ideal.The effect of compound m...