Abstract: On the basis of previous work，further study on the influence of the addition of (NH4)2SO4 on quinoline denitrogen efficiency was conducted and under the best operation conditions for quinoline denitrogen, the denitrogen bacterium HY9 cultivated in nutrients was tested for nitrogen removal from diesel fuels. Experimental results show that inorganic nitrogen has no influence on the degradation of quinoline. The proportion of nutrients to diesel oil has little effect on diesel oil denitrogen and the best proportion is 1.5:1. The ratio of diesel oil denitrogen is increased from 12.9% to 16.7% when the surfactant tween80 is added at the optimal ratio of 0.175 g Tween80/25 mL diesel oil. Higher shaking speed improves the nitrogen removal efficiency as it can reduce the size of oil-water drop to dissolve more oxygen. The shaking speed tests show that the optimal conditions are 3 mL of suspension of HY9 cultivated and 250r/min with a denitrogen ratio of 19.5%. However，the times have no effect on efficiency of denitrogen.

Key words: quinoline , bacterial strain, isolation, diesel oil, degradation