Au nanoclusters, stabilized by PVP, catalyze the aerobic oxidation of p-HBA. In this study, its principal reaction route was analyzed using Au-38. First, the arrangements of substrates, including ligands, were estimated. Next, these ligands were replaced with negative point charge of -1, and each system was re-optimized. The results obtained from these models exhibited the same tendency for the two reaction pathways. By estimating the electron density transfers between the substrates and oxidants, it was suggested that the electron affinity of the active oxygen species and Au NC is a good index for determining the main reaction pathways.