In order to understand the molecular structure of coal and the mechanism of coal direct liquefaction, the heavy intermediates of coal liquefaction such as asphaltene (AS) and preasphaltene (PA) were separated into different sub-fractions by column chromatography, respectively. The distributions of fused aromatic nucleuses (FAN) of sub-fractions were determined by synchronous fluorescence combined with the fitting technique of multiple peaks of spectrum. The results indicated that the PA and AS obtained from liquefactions of three Chinese coals were separated into 4 and 2-4 sub-fractions, respectively. The content of three rings FAN was the highest in the major sub-fractions of AS. The major sub-fractions of PA contained not only more single ring aromatic nucleus but also larger FAN than those of AS. Meanwhile, there were more complex aggregations in PA compared to AS. (C) 2012 Elsevier Ltd. All rights reserved.