The hydrogenation reaction of several common coal related model compounds was simulated using the ReaxFF MD method. The results showed that the active sites for the hydrogenation initiation reaction were not only related to the superdelocalizability (S-r), but also related to the steric hindrance effect. Since the activation energy required was low, the hydrogenation initiation reaction mainly occurred at the aromatic ortho-position of substituents even if the hydrogenated free radicals formed by H-center dot attaching to the substitution site was more thermodynamically stable. This indicates that the hydrogenation initiation reaction was mainly controlled by kinetics. The hydrogenated products observed in the ReaxFF MD simulation were analyzed. It was found that the ReaxFF MD simulation results were consistent with the experimental results for hydrogenation in a sulfur-free system. Therefore, the ReaxFF MD simulation provides an effective approach towards the study of the hydrogenation reaction at a molecular level. (C) 2015 Elsevier Ltd. All rights reserved.