A method for speciation analysis of polycyclic aromatic sulfur heterocycles (PASHs) in crude oil was established. The PASHs were separated from the oil sample by ligand exchange chromatography using SiO 2 with PdCl 2. The sulfur compounds were then determined by gas chromatography using a mass spectrogram detector (GC/MS), gas chromatography with a sulfur chemiluminescence detector (GC-SCD), and chromatography retention index of the compounds. More than 100 PASHs (including alkyl benzothiophene, dibenzothiophene, and alkyl dibenzothiophene) were identified. The dibenzothiophene and alkyl dibenzothiophene represent about 91 % of the total PASHs in crude oil. The method can be applied for speciation analysis of PASHs in crude oils from different sources.