The irradiation effect on ,Aspergillus oryzae, spores was studied by 0.54keV X-rays (about the K shell absorption edge of oxygen) from the synchrotron facility at NSRL. A high production mutant for kojic acid was obtained from the spores irradiated by soft X-rays, which accumulated 27.79g kojic acid per L in 500mL shake-flask fermentation for 10 days using glucose as carbon source, and has increased about 56% of production than that of the original (17.81g/L). Also the fermentation conditions were studied with different carbon sources and nitrogen sources. The results showed that the mutant induced by the X-rays of synchrotron radiation would be of potential for high kojic acid production.