The degradation dynamics of phenanthrene in soil was studied. The half-life of phenanthrene in the non-sterilized contaminated soil was only 5.1 d, much shorter than the same in the sterilized soil. The dominant strain of phenanthrene microbial degradation was isolated and identified by 16S rDNA as Alcaligenes sp.; its growth and degradative capability were highest at 25°C and pH of 7.0. Inoculation of the dominant strain to soil enhanced phenanthrene degradation, and faster degradation rates were observed with larger doses of the strain inoculated.