Direct coal liquefaction (DCL) is one of the effective ways for coal-hydro conversion and directional production of high-quality fuels and high value-added chemicals. The direct coal liquefaction process is a complex reaction system composed of coal,hydrogen,solvent and catalyst,involving the material transfer and reaction of gas phase,liquid phase and solid phase. While the solvent acts as hydrogen source during DCL,the catalyst promotes the hydrogenation of macromolecules and thermal cracked fragments of coal. How to effectively coordinate and play the role of catalyst and solvent in coal hydrogenolysis reaction will determine the structure composition and yield of liquid products of coal hydrogenolysis reaction. The pyrolysis of typical model compounds in coal,such as aromatics,alkylaromatics,and hydrocarbons having sulfur/oxygen/nitrogen/halogen,etc. was summarized,and the changes observed on the physicochemical properties of these compounds in common solvents,heavy oil solvents and organic waste solvents were discussed,which might affect the subsequent hydrogen-assisted liquefaction. The mechanism of solvent swelling,hydrogen transfer and hydrogen supply to coal was analyzed. A brief introduction was given on the free radical reaction and catalytic liquefaction mechanism occurring during the DCL. The role and status of various DCL catalysts such as metals,metal oxides,metal sulfides,and solid acids (e. g. metal halides and others) were described with a special emphasis on iron-based catalysts. Then,the possible synergistic effect of solvent and catalyst in the hydrogen transfer process of direct coal liquefaction process was discussed. This effect can not only promote the coal hydrogenolysis reaction,improve the yield of direct coal liquefaction oil,but also adjust the structure of liquid products. Finally,in order to further improve the yield of coal liquefaction,the specific research contents and methods in strengthening the synergistic effect of solvent and catalyst were put forward.