Based on eight kinds of active group obtained from experiments, novel molecular models of coal are proposed for investigating the mechanism of oxidation of coal at room temperature. The optimized geometries of simulated coal molecules and the thermodynamic data of the species were obtained by DFT-B3LYP and ONIOM methods. The mechanism of initial oxidation at room temperature for each simulated coal molecule is presented and the activation energies of the reactions are calculated. The order of activity of these active groups and the other computational results are in agreement with experiments. (c) 2004 The Combustion Institute. Published by Elsevier Inc. All rights reserved.