Compared with traditional pyrolysis processes, the integrated process of CO2 reforming methane and coal pyrolysis (CRMP) can obviously improve the tar yield. However, the structural information and formation mechanism of coal tar in the integrated process are still unknown. To compare the chemical composition of coal tars under different atmospheres, GC and GC/MS were used to analyze the volatile fractions of tar obtained by pyrolysis of Shendong coal at 750 degrees C in CRMP process and to be compared with those under nitrogen, hydrogen, methane, carbon dioxide atmospheres. The results show that phenol and its alkyl-substituted homologs from C-1 to C-3 are the major products of the volatile fractions (distillate below 300 degrees C). H-1 NMR and C-13 NMR analyses of coal tars show that the tar derived from CRMP process is mainly composed of alkyl-substituent attached to aromatic ring. The mechanism analysis of CRMP process indicated that the increase in tar yield of CRMP process should be attributed to the free radical reaction. (C) 2010 Elsevier Ltd. All rights reserved.