Abstract: The influence of coal tar distillates on coke formation during the processing of Liaohe heavy crude oil with the distillates was studied.The composition of feedstock was characterized by the elemental analysis,the proton nuclear magnetic resonance spectrometry,the synchronous fluorescence spectrometry and the group analysis techniques.It has been found that the coke formation of Liaohe heavy crude oil upon heating can be reduced by co-processing with the coal tar distillates.Under the experimental conditions,the coke yields from the co-processing(0.5%-5.9%) are lower than that from the weighted calculation(3.3%-6.4%);a positive synergetic effect was observed.The extent of the synergetic effect depends on the chemical composition and content of the distillates.Saturates,1-ring aromatics and condensed 4-ring aromatics may retard the coke formation,whereas 2-ring and 3-ring aromatics as well as condensed 2-ring aromatics may retard the coke formation.