Abstract: Ten alpha-amylase producing Bacillus strains were isolated from soil （four strains）, water （three strains） and flour （three strains） through isolation with starch plates, Gram＇s staining and spore staining. The ratio of hydrolysis zone diameter to colony diameter was 1.9-2.6. Liquid culture medium was used for fermentation to produce amylase. The activity of alpha-amylase was determined by colorimetry, and it was 4.8-5.7 g/mL in fermentation broth. The original strains producing high-activity alpha-amylase was selected and mutated by UV mutagenesis. Excellent strains were obtained, and their activity of alpha-amylase was up to 9.6-13.0 g/mL under suitable conditions, which was 69.9%-129.5% higher than that before selection.