Abstract:  Co-liquefaction of coal and polystyrene (PS) in supercritical water (SCW) was studied in an autoclave. The experiments were carried out to investigate the effects of water to reactant ratio(10~30) (mass ratio), temperature (360℃~430℃) and the addition of plastic（10%~40%）(mass ratio) on the coal conversion, yields of asphaltenes, oil and gas. The results show that with the increasing ratio of water to reactant, the total coal conversion increases at first and then remains constantly; while the yield of oil and gas keeps increasing. The conversion of coal and the yield of oil and gas increase dramatically with the temperature increasing above 420℃. It is found that the conversion reaches the maximum value as 31.2% at 430℃, while the yields of oil and gas, asphaltenes are 12.6% and 18.6%, respectively. The yields of oil and gas for co-liquefaction of coal and plastic are higher, typically by 0.6%~2.7%, than the weighted average oil and gas yields for the coal and plastic alone, which implies the synergistic effects on coal conversion.