Abstract: In view of the bioremediation oil-contaminated soil in low-temperature areas, the low-temperature resistant petroleum hydrocarbon degrading bacteria group X-3 was selected from Xinglongtai soil sample of Liaohe Oilfield and was identified by 16S rDNA sequence analysis. It was found that X-3 included 2 Pseudomonas sp., 1 Arthrobacter sp., 1 Rhodococcus sp., 2 Bacillus sp., and 1 Ochrobactrum sp. The culture conditions of X-3 were optimized through experiments. The results showed that under the conditions of temperature 10-15 ℃, the inoculation amount was 3% (mass percent), the optimum concentration of petroleum hydrocarbon was 10 g·L^–1, and the optimum nitrogen phosphorus ratio was 10∶1. Under the condition of the optimum pH value of 7, the degradation rate of petroleum hydrocarbon by X-3 increased from 47.75% to 60.07%. GC-MS analysis of petroleum hydrocarbon components before and after degradation showed that X-3 could biodegrade the n-alkanes ranging from C₁₀to C₂₀ to a certain extent and the utilization rate of petroleum hydrocarbon by degrading bacteria decreased gradually with the increase of carbon atom number, in which the degradation rate of C₁₆—4CH₃ was only 25%, indicating that the biodegradation of branched hydrocarbon pollutants was more difficult than that of straight chain alkanes.