In order to find the optimal operating parameters in high-temperature and low-temperature coal tar hydrocracking processes and to maximize the light oil yields, experimental studies have been carried out in a one-stage reactor in supercritical solvents. Xylene and gasoline were used as supercritical solvents to investigate their effects on the light oil yields. The results show that gasoline was more suitable as a supercritical solvent and that a suitable ratio of gasoline solvent to coal tar could result in higher light oil yields in both high-and low-temperature coal tar hydrocracking processes. The effects of different operating parameters, including temperature, hydrogen pressure, catalyst, and residence time, on light oil yield were tested. It was found that the yields of light oil from the two coal tar hydrocracking processes varied with the operating parameters in a similar manner. However, different values of the operating parameters gave rise to the maximum yields of light oil from the respective processes. (C) 2011 Elsevier Ltd. All rights reserved.