Abstract: Coal and residuum are first co-pyrolyzed, and then hydrogenated into small molecule products during co-liquefaction. Therefore, clarifying influence of residuum on coal pyrolysis performance is an important thermochemical basis for regulating the process. The co-pyrolysis behavior of atmospheric residuum (AR) and Naomaohu coal (NMH) were investigated by TG, TG-FTIR and distributed activation energy model. The results showed that the peak temperature of the maximum rate of weight loss for the co-pyrolysis process was reduced by 7 °C compared with the theoretical value calculated by weighted average of AR and NMH pyrolysis alone, while the weight loss increased by 3%, the average activation energy decreased by 23.6 kJ/mol. In addition, the peak area of alkyl O-containing functional groups such as alcohols and ethers increased, whereas those of CO and CO₂ decreased, suggesting that AR had a positive effect on NMH pyrolysis. Meanwhile, alkyl radicals from AR decomposition would combine with O-containing radicals generated from coal pyrolysis, thus resulting in a decrease of CO and CO₂ by inhibiting breakage of carboxyl groups. This work will provide a scientific evaluation basis for revealing the influence of residuum on composition of coal liquefaction product during co-liquefaction.