A bacterium strain, which prove to be highly effective in phenol degrading, was isolated from soil contaminated with oil in Jingbian oilfield of Northern Shaanxi by using enrichment culture method with phenol as a sole carbon source. The bacterium was named ad049 and identified as Rhodococcus on the basis of the morphological characterizations, physiological and biochemical identification, and alignment analysis of the 16S rDNA sequence. Effects of inoculation quantity of ad049, pH, temperature, and concentration of phenol as a substrate on bacterial growth and the efficiency of ad049 on phenol degradation were also investigated by shaker culture method, and dehydrogenase and catechol dioxygenase were determined as well. Results showed that the ad049 had a strong biodegradation capability for phenol. It degraded 99% of the phenol in a concentration of 1000 mg/L in 24 hours under the incubating condition of 30 ℃, pH 8, and 5% of ad049 inoculation. The degradation process could be described with zero order kinetics equation with the k₀ and R² values of 41.51and 0.96, respectively. The degradation of phenol by ad049 might be achieved largely by 1,2-dioxygenase for ortho ring opening of benzene, and partly by catechol 2,3-dioxygenase for meta-cleavage.