Co-liquefaction of Banpoo coal and used grease has been studied in a batch reactor at a temperature range of 370-450 ํC, 5-9 MPa of initial hydrogen pressure, 1:9-6:4 of coal:grease ratio and reaction time of 30 min. The two level factorial experimental design was performed to investigate the effects of process variables of liquid yield. The process variables are temperature, pressure and coal:grease ratio. It was found that liquid yield was significantly affected by coal:grease ratio and temperature. From a study of temperature effect, the change of liquid distribution was also found. At the optimum condition of 370oC, 5 MPa and coal:grease ratio 6:4, conversion and liquid yield reached 63 and 27%, respectively. By adding Mo(CO)[subscript 6], Fe[subscript 2]S[subscript 3] and ZnCl[subscript 2] catalysts, no effect of catalysts on the change of liquid yield was found. The maximum liquid yield reached 55% at 370 ํC of temperature and conversion was obtained 64% for co-liquefaction in supercritical toluene-tetralin (70:30 v/v).