The spore suspension of ascomycin producing strain Streptomyces hygroscopicus was mutated by ultraviolet(UV) and atmospheric and room temperature plasma(ARTP), and a high-yield mutant strain Streptomyces hygroscopicus FIM-38-24 was obtained through primary screening and rescreening by flask shaking fermentation. The content of ascomycin was determined by HPLC. The results showed that the ascomycin production capacity of the mutant FIM-38-24(568.0 μg/ml) was 4 times of that of the original strain.