Soil hydrogen-oxidizing bacteria can utilize soil gaseous hydrogen as an energy source to assimilate carbon dioxide. In this paper, a gas-cycle incubation system (H2 treatment system) which can provide stable H2 flow (41.6-125 micromol x L(-1)) via H2O electrolysis was developed, and a mineral salt agar medium (MSA) was used to separate the hydrogen-oxidizing bacteria in soybean rhizosphere. A total of 40 bacterial strains were isolated from the incubation system, and their hydrogen uptake was measured. 20 of the strains could utilize hydrogen and grow autotrophically, which were preliminarily identified as hydrogen-oxidizing bacteria. Their colony form and physiological-biochemical characteristics were studied.