In order to develop a more efficient method for deep denitrogenation of the liquid hydrocarbon streams and fundamentally understand the denitrogenation mechanism, identification and quantification of various nitrogen compounds in the liquid hydrocarbon streams are essential. In the present study, identification and quantification of various nitrogen compounds existing in four typical samples (straight run gas oil (SRGO), light cycle oil (LCO), coal-derived liquid (CDL) and ultralow sulfur diesel (ULSD)) were conducted by a combination of the pre-separation of the nitrogen compounds, gas chromatography with a mass detector (GC-MS) and gas chromatograph with a nitrogen phosphorus detector (GC-NPD). The results show that the nitrogen compounds in different liquid hydrocarbon streams are quite different. The major nitrogen compounds remaining in LCO and ULSD are carbazole and its alkyl-substituted derivatives, while in CDL are the basic nitrogen compounds, including pyridine, aniline and quinoline and their derivatives. The determined type and distribution of the nitrogen compounds in the different streams provide essential information for development of new methods or adsorbents to remove the nitrogen compounds from various liquid hydrocarbon streams.