A pyrene-degrading bacterium strain named PW was isolated from the soils contaminated with polycyclic aromatic hydrocarbons (PAHs) in Beijing Coking Plant using an enrichment culture. It was identified according to its morphology and molecular biology analysis. This bacterium belongs to the strain Ochrobactrum sp. This strain was domesticated for a period of time by a large dose method, and then shake flask experiments were used to study the influence of environmental conditions on the degradation extent of pyrene. The results showed that after domestication the degradation extent increased from 62.3% to 92.7% on the 5th day. The bacterium strain PW could degrade pyrene at temperatures ranging from 20 to 40℃, and the degradation extent at 30℃was the highest. The degradation extents were above 45% in cultural mediums at a wide range of pH from 5 to 10. The results also indicated that the pyrene degradation could be affected by salt concentration and the degradation effects were better when the mass fraction of NaCl in the culture medium was less than 3%. Further study showed that the strain PW could was resistant to high concentrations of some heavy metal ions.