The nitrogen-containing compounds in Huadian shale oil (HDSO) produced by pyrolysis of Huadian oil shale at the final temperature of 520 degrees C in a fixed bed reactor were characterized in detail by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS). We find that HDSO contains six basic nitrogen classes, but the other basic N2O1, N2O2, N-3 and N3O1 classes determined in US Western shale oil (USSO) and Russian Slanet shale oil (RSSO) are not found in HDSO; while the neutral nitrogen classes are almost the same as those in USSO and RSSO. The basic N-x classes predominate in all basic classes in HDSO, and the relative abundance of the basic N-1 class is much higher than that in USSO and RSSO. In HDSO most basic N-1 and N1O1 class species consist of the nitrogen-polycyclic aromatic compounds with 1-7 aromatic rings and 0-42 carbon atoms of the alkyl side chains; while the major neutral N-1 and N1O1 compounds identified contain 1-5 aromatic rings and 0-35 carbon atoms of the alkyl side chains. Furthermore, pyridines and tetrahydroquinolines which contain 15-28 and 11-24 carbon atoms of the alkyl side chains respectively are dominant in all basic nitrogen species; indoles and carbazoles are the most abundant in all neutral N-1 species. The N1O1 species containing 1-4 aromatic rings and 1-24 carbon atoms of the alkyl side chains are relatively abundant. Most likely a substantial amount of the N-2 class species identified in HDSO are azaindoles and azaquinlines series. Crown Copyright (C) 2012 Published by Elsevier Ltd. All rights reserved.