3-(p-methyl)anilinomethylidene-6-aryl-5,6-2H-dihydropyran-2,4-dione was selected as the model reactant compound to study the catalytic hydrogenation of 3-anilinomethylidene-6-aryl-5,6-2H-dihydropyran-2,4-diones by the AM1 semi-empirical method. Molecular information such as net charges, bond orders, values of frontier orbital energies, composition, proportions and bonding contribution was acquired and analyzed. Thus, possible reactive sites were proposed and the reaction mechanism was postulated via two different pathways. The postulated intermediates and products were also computed using the AM1 method. Their heat of formation values and energies of HOMO/LUMO/SOMO indicate that the mechanism of catalytic hydrogenation of 3-anilinomethylidene-6-aryl-5,6-2H-dihydropyran-2,4-diones is hydrogenolytic cleavage on a dihydropyrandione ring, not the simple addition of a CyC double bond. Therefore, the experiment result is elucidated theoretically.