A mutant strain UV21012-1 producing Kojic acid was obtained from the start strain Aspergillus oryzae 2336 treated with ultraviolet irradiation twice.This mutant strain exhibited good genetic stability in the procedure of successive inoculation and fermentation. The kojic acid productivity of the UV21012-1 increased by 1. 68 times compared with that of the start strain. Meanwhile, the fermentation period of UV21012-1 was shorter than that of the start strain.