Abstract The pyrolysis of Huolinhe lignite under CO2 atmosphere was carried out in a thermobalance and a fast heating-up fixed bed reactor. The distribution of gases, char yield and its property such as element, surface structure, FT-IR spectra were analyzed. By this, the effect of CO2 on the pyrolysis behaviors was studied. The results show that CO2 gasification of the nascent char, which destroys the hydrogen-containing char structure, not only promotes cracking of benzene ring and fracture of hydroxyl, methyl and methylene groups etc., but also weakens the interaction between H and char matrix and increases the H fluidity, leading to the increase in the generation of H radicals. These H radicals can combine with other free radical fragments generated from fracture of the coal macromolecules to produce more volatiles. This will produce the char with a high specific surface and high pore volume and porosity. The introduction of CO2 promotes the coal pyrolysis and generation of volatile, resulting in decrease in char yield and increase in the evolution amount of H2, CO, CH4 and other small molecules hydrocarbons.