Abstract: Coal and char are essential energy sources for the process industry. Insightful understanding of those molecules is useful to explore reactivities of coal and char. Therefore, coal and char molecular structures were investigated at atomic level using Materials Studio 7.0 software. Firstly, coal and char initial structures were constructed based on reported literatures. Secondly, those structures were improved by molecular mechanics, where functional group fragments were added to satisfy the property of coal or char. Then, the subsequent structures were optimized by annealing dynamics simulation to adjust density and elementary composition. Finally, the potential energies of coal and char were calculated using energy minimization method. It was pointed out that the estimated densities and elementary composition were agreements with the published literatures, which indicated that those structures were valid and reasonable. From the simulated results, it was shown that the Coulomb energy and van der Waals energy played a much more important role than other energies during the stabilizing molecular construction process. Thus, it was inferred that the weak bond was predominant in the thermal processing of coal or char. In addition, this work demonstrated that the molecular simulation technology was meaningful to construct the complex macromolecular structure.