A Huo linhe coal sample and its N-2-devolatilized char have been pyrolyzed in a pressurized fixed-bed reactor under N-2 and 50% CO2/50% N-2 atmospheres, respectively. With a view to avoiding any disturbance from the devolatilization process, N-2-devolatilized char was used to study the effect of CO2 on the cleavage of chemical bonds. The results show that CO2 intensifies the consumption of H in the char before its release in the form of H-2. More H in the char is transferred into gaseous aliphatic hydrocarbons and condensable volatiles, leading to a decrease in the yield of H-2 under 50% CO2 atmosphere compared with that under N-2 at elevated pressure in the range 550-900 degrees C. A CO2 atmosphere is the dominant factor in the release of H from char below 700 degrees C, such that more H in char induced by CO2 is transferred into volatiles at 550 degrees C than that at 800 degrees C, above which temperature controls the release of H from char. Thus, CO2 induces the decomposition of more H-containing organic groups to form CH4, C2H6, C2H4, and H-rich low-molecular-weight tar at elevated pressure and 550 degrees C. Dissociative adsorption of CO2 on coal/char can generate adsorbed active C(O) and active C-f at elevated pressure. The electronegativity of the O in active C(O) induces cleavage of adjacent bonds, and the formation of active C-f may induce new structural defects or active sites (C-f) capable of inducing bond cleavage, resulting in the cleavage of chemical bonds in the char at lower temperatures than under N-2 atmosphere at elevated pressure, such as those of aromatic rings, aliphatic chains of aromatic hydrocarbons, and ether bonds.