Abstract: Global energy shortage and the high cost of chemical fertilizer make the research of biological nitrogen fixation become necessary and urgent. Research on the breeding and biology of nitrogen-fixing bacteria is the base for nitrogen-fixing microbial fertilizer industry. A nitrogen-fixing bacillus strain GD272 was isolated and its morphology, physiology and chemical properties were studied. Identification with 16S rDNA sequencing, morphology, physiology and chemical properties showed that strain GD272 is Bacillus sp. Relative high nitrogenase activity of GD272 was determined with acetylene reduction assay. Green house test indicated that pakchoi inoculated with GD272 grew as well as those supplied with chemical nitrogen fertilizer. Strain GD272 shows a good prospect in nitrogen fixing microbial fertilizer production.