Twenty three single colonies of actinomycetes were isolated from a soil sample collected from Changshu Agroecological. Experimental Station,Institute of Soil Science,Chinese Academy of Sciences Among 10 strains distinguished from each other by morphological properties,9 were further identified as Streptomyces sps. All strains showed capability of reducing nitrate into N₂O under anaerobic pure culture conditions. Three strains were selected and denitrification rates were measured. Nitrous oxide product ion rate of these strains ranged from N 1.2 to 187.7 g g^-1 min^-1. The strains were shown not only to grow well but also to be able to reduce nitrate to N₂O in sterile soil,indicating that these strains were able to use soil organic carbon as electron donor for nitrate reduction. Acetylene showed inhibitory effect on N₂O production of most strains isolated. Stressed under continuous strict anaerobic condition,strains of Streptomyces sps still showed considerable denitrification capacities.