Different kinds of mineral nutrients( NO3-N, NH4-N and PO4-P) were applied in the simulated oil-polluted seawater for enhancing oil biodegradation in the N/P ratio 10:1 and 20: 1. Although indigenous microorganisms have the ability to degrade oil, adding nutrients accelerated biodegradation rates significantly. For the group amended with NO3-N and PO4-P in the ratio 10:1, the reaction rate coefficient was 4 times higher than the natural biodegradation. Chemical and microbiological analysis showed that the optimal N/P ratio in the system is 10:1, and microorganisms tend to utilize nitrate rather than ammonium as N source.