A cold-resistant bacterium (strain GYT1) for degrading nitrobenzene was isolated from sediment in the Wei-he River by cultivation, domestication, enrichment, screening, and purification. Strain GYT1 is observed as a gram-negative bacterial strain of short pole shape according to the analysis of its morphology and physiological-biochemical characteristics. Strain GYT1 is identified as Methylobacillus sp. Lap based on the similarity analysis of its 16S rDNA gene sequence with the sequences logged in RDP database and the GenBank. Methylobacillus sp. Lap has never been reported to be able to degrade nitrobenzene. The degradation characteristics show that strain GYT1 can grow with nitrobenzene as the sole source of carbon and nitrogen. Nitrobenzene can be degraded completely when nitrobenzene concentration is less than 711μg/L at 12±0.5ºC, with 15ml inoculation volume of strain GYT1 and pH 6.3-7.2. The degradation process meets the first-order reaction dynamics. According to the results of GC-MS analysis, nitrobenzene can be degraded into small molecule substances of non-toxicity or low-toxicity, and finally into CO₂ and H₂O by multi-step biochemical reactions under the action of enzyme catalytic metabolism.