Co-pyrolysis of Huainan coal (HN) and its distillation residue of the primary coal tar (DRPT) was carried out in a tubular furnace. The experimental results show that the pyrolysis tar yields are 3.74%-1.48% (relatively) higher than the calculated values from blending ratios of DRPT:HN = 1:100 to 5:100, and decrease by 0.95% (relatively) at DRPT:HN = 10:100. The n-hexane-soluble fraction (nHS) in pyrolysis tar is 5.22%, 6.30%, 6.81% and 6.63% higher than the corresponding calculated values at proportion of DRPT:HN = 1:100, 3:100, 5:100 and 10:100, respectively. The pyrolysis residue (PR) yields are negatively affected by adding DRPT to HN. To further investigate the interaction mechanism between HN and DRPT during pyrolysis, thermogravimetry (TG), gas chromatography (GC), hot stage microscopy and electron spin resonance (ESR) techniques were applied to analyze the behavior of their co-pyrolysis. It is found that there are significant interactions between HN and DRPT in co-pyrolysis and the pyrolysis tar and light oil yields are evidently increased by blending DRPT. (C) 2015 Elsevier B.V. All rights reserved.