Screening with enzyme activity and biomass of cell, two mutants (UV-A and UV-B) were obtained from Aspergillus oryzae sbb201 that have been treated with ultraviolet joint lithium chloride mutagenesis. These two parent protoplasts were inactivated with ultraviolet and thermal method respectively, and then fused by PEG induction. A mutant strain was finally obtained which has showed a higher activity of fructosyl-transferase. The enzyme activity reached 172.95 U/g, increased by 64.57% compared with that of the original strain.