The effect of hydrotreatment of liquefied heavy oil on direct coal liquefaction (DCL) was studied by hydrogenating the liquefied heavy oil (initial boiling point greater than 320 degrees C) in a 30 ml continuous hydrogenation apparatus at operating conditions of pressure (P) 13-19 MPa, temperature (T) 360-400 degrees C, liquid space velocity (LHSV) 0.6-1.4 h(-1). After hydrogenation, the properties and hydrocarbon composition of liquefied heavy oil were regulated, leading to the enhancement of hydrogen donating ability and 5.6% increase in oil yield of DCL as compared with non-hydrogenated raw oil. Based on the results, a new method of preparing recycle solvent for direct coal liquefaction by mixing hydrogenated heavy oil and un-hydrogenated middle oil in a suitable proportion was proposed, which has been verified to be effective and efficient to increase oil yield. (C) 2017 Elsevier Ltd. All rights reserved.