Proteus volgaris was isolated from costal sea water of Lattakia city port, as it is contaminated with petroleum compositions coming from marine transportations activities. The ability of this bacteria to degrade the petroleum alkanes was studied by using different concentrations of petroleum as sole source of carbon and energy. The gas chromatography (GC) technique was used to measure the concentration of alkanes. Results showed that the isolated bacteria were able to degrade different alkanes chains. The ratio of biodegradation of C12, C16, C18 were 96.75%, 78.59%, 97.27% respectively, while the rate of biodegradation of the entire amount of alkanes was 77.14% in 10 mg/ml polluting concentration. The percentage of biodegradation at concentration 75 mg/ml of petroleum was 17.26%. Therefore, the high ability of Proteus volgaris to degrade the long chains alkanes recommended it to be effective in the bioremediation process of the contaminated marine environments.