In order to explore assembly mechanism of soil bacterial community, we performed sterile soil inoculation experiments using two distinct soils, sampled from a nitrogen fertilized cropland and an aromatic compounds contaminated industrial site respectively. Sets of soil sterilized with γ-radiation were reciprocal inoculated with a subsample of unsterilized soil. After two months’ incubation with different inoculation-dose and oxygen condition, the soil bacterial richness and community structure were measured by 16S rRNA gene V3-V4 region sequencing.