The invention discloses ferrocene ion liquid and a synthesis method and application thereof. The ferrocene ion liquid is prepared by using ferrocene as a raw material through a series of reaction and comprises 1-ferrocenylalkyl-3-alkyl imidazole salt and 1-ferrocenylalkyl-2-alkyl-3-alkyl imidazole. The prepared ferrocene ion liquid has a removing effect on neutral nitrogenous compounds, i.e. benzpyrole in diesel to different extents and is expected to become denitrifying agent for the neutral nitrogenous compounds in the diesel.