A strain ZG0656 producing a-amylase inhibitor was isolated from soil in this study. Polyphasic taxonomic studies were performed, including appearance characteristics, culture characteristics, phenotypic characteristics, cell walls chemical composition, nearly complete 16S rDNA sequence alignment with those of representative Streptomyces species. These results revealed that strain ZG0656 represents a novel variation of Streptomyces coelicoflavus, for which we propose the name S. coelicoflavus var. nankaiensis. After fermentation in a 10 L fermentor, alpha-amylase inhibitors were accumulated in the harvested broth of strain ZG0656. The alpha-amylase inhibitors we obtained were identified as aminooligosaccharides after concentration, resin-adsorption, gel-filtration, and desiccation. They could intensively inhibit alpha-amylase, depress postprandial blood glucose elevation obviously. Thus, the a-amylase inhibitors are expected to act as drugs or functional food against diabetes.