One novel extraction process for denitrification of fuel based on ionic liquid was developed. Influence of water on this process was systematically investigated. The mechanism of this process was illustrated by density functional theory (DFT) calculations. The optimized extraction parameters were obtained by a series of experiments, such as mass ratio of ionic liquid and the initial N content. Meanwhile, [Bmim]BF4 was recycled through rotary evaporation, and exhibited good recycling properties and extraction efficiency. Finally, a specific separation process and technology was proposed based on the experimental data.