Abstract: Using plate dilution method, seven hundred and eighty-nine strains were isolated and purified from the diffrent vegetable soil samples collected from the suburban districts. By pairing culture, 12 strains had apparent antagonistic effect to Pythium ultimum, ca. 2.67% of all tested strains showed antagonism, whose radius of suppression cycles was between 3.1~16.4 mm. By selected medium method, nine strains producing siderophore were obtained. Qualitative and quantitative analysis showed that different strains had different ability producing siderophore, but the result of two methods was consistant. pH value had a direct effect on absorbance of siderophore, absorbance declined to shortwave under excessive acidic and alkaline pH conditions, while to longwave under neutral pH conditions. It had three absorbance apexes and got to maximun, which were 224.0 nm, 264.0 nm and 400.0 nm, respectively under pH8.3. Effect of bacteria producing siderophore on cucumber growth showed three actions,which were promotion, inhibition and no action, respectively.