The non-catalytic partial oxidation of hot coke oven gas (HCOG) was numerically simulated using a detailed chemical kinetic model and a completely mixed batch reactor model. The kinetic model was primarily based on that developed by Richter and Howard [Phys. Chem. Chem. Phys. 2002, 4 (11), 2038−2055], including more than 200 chemical species and more than 2000 elementary-step-like reactions. The HCOG was modeled as a multi-component gas mixture involving H2, CO, CO2, CH4, C2 hydrocarbons, H2O, and 31 aromatic hydrocarbons, such as benzene and toluene, as well as polycyclic aromatic hydrocarbons up to coronene, to represent the HCOG tar. The effect of oxygen addition in the inlet gas mixture was investigated at oxygen concentrations from 0 to 15 vol %. The simulations indicated that oxygen was consumed almost completely for the combustion of reactive light gases, such as H2 and CO, and light hydrocarbons, such as CH4 and C2H6, within a reaction time of a few tens of milliseconds when the inlet gas temperature was 1173 K. In reforming the tar involved in HCOG, the primary role of oxygen should be to induce temperature increases of the reacting gas by combustion, thereby accelerating the subsequent reforming of the tar by steam. A reaction pathway analysis suggested that the co-existence of oxygen and aromatic hydrocarbon radicals was necessary to decompose aromatic compounds into compounds of lower molecular mass.