The two-stage co-processing of coal with medium-density polyethylene (MDPE) was investigated using ammonium tetrathiomolybdate (ATTM) as a catalyst. The first-stage plastic pyrolysis carried out at 420 °C, 6.0 MPa hydrogen pressure and HZSM-5 as catalyst. The second-stage coal and MDPE co-liquefaction had been performed in a hydroprocessing unit at 430 °C and 6.0 MPa hydrogen pressure with ATTM catalyst. A competitive experiment was performed by the way of one stage co-liquefaction of coal with MDPE using ATTM as catalyst and tetraline as solvent. The aim of the experiments was to determine the effect of the use of the waste plastic pyrolysis product as solvent. The results indicate that the hydroprocessed liquids of both the one stage and the two-stage co-processing of coal with MDPE have about 70% of compounds with boiling point below 350 °C, and meet the sulphur and nitrogen specifications for refinery feedstocks.