Single-atom catalysts possess novel and unique properties and excellent catalytic activities because of their distinct geometric and electronic structures. In this study, we investigated the catalytic mechanism of the cyclohexanone hydrogenation by Pt@Na₃PMA (PMA = PMo₁₂O₄₀³⁻) using density functional theory calculations. Our findings indicate that the potential anchoring site for a single Pt atom is a fourfold hollow site on PMA. The bonding interaction between Pt and PMA arises from both ionic and covalent interactions of the Pt−O bond. The calculated adsorption energy suggests that the coadsorption of H₂ and C₆H₁₀O molecules on Pt@Na₃PMA exhibits high thermal stability. Furthermore, we proposed a catalytic cycle for the hydrogenation of cyclohexanone by Pt@Na₃PMA, demonstrating that the hydrogenation of the carbonyl oxygen atom in cyclohexanone is the rate-determining step. Throughout the reaction, Na₃PMA acts as an “electron sponge”, for accepting and donating electrons. It is expected that the results presented in this work will provide valuable insights into the hydrogenation of cyclohexanone.