This paper reported the results of mutagenesis by nitrogen plasma radiation with energy from 65 to 80 keV and dose from 9.6×10,9, to 1.5×10,11,/cm,2, in antineoplastic antibiotics daunorubicin—producing S. Coeruleorubidus. The relationship between death rate and radiation dose was formulated by computer and the formula. It was fit to a biological single — hit curve. The obtained high—producing mutagenic strain 137 was tested for its production property. The result showed that it could increase the daunorubicin potency by 25.8% in productive tanks of fermentation.