Abstract: The coal tar heavy oil was pre-hydrotreated and then characterized by means of infrared spectroscopy，nuclear magnetic resonance and elemental analysis. The physicochemical properties and the hydrogen supply ability of the pre-hydrotreated oil were investigated from the molecular structure point of view. The results showed that after the aromaticity of the hydrotreated heavy oil decreases from 0.89 of feed to 0.80, the degree of substitution of aromatic rings increases from 0.12 to 0.20 and the hydrogen supply index （PDQI） increases from 3.21 to 4.02. The hydrogen consumption of coal tar heavy oil in coal-oil co-processing from 4.03% to 3.74%，the conversion rate and the oil yield are improved，the asphaltene content in the product decreases significantly, the oil quality is greatly improved .

Key words: coal tar heavy oil, pre-hydrotreating, coal-oil co-processing, hydrogen supply performance