The effects of additive metal ions on photo-catalytic oxidation (PCO) of phenol in aqueous solution was studied on a bench scale using Ti $O_2$ and UV as the PCO system. It was considered that ferric ion (F $e^{3+}$) and ceric ion (C $e^{4+}$ could increase the efficiency of degradation of phenol in PCO reaction, only if F $e^{3+}$ and C $e^{4+}$, as electron acceptors, could prevent the recombination of hole-electron in the surface of Ti $O_2$. From the quantitative investigation, it was found that ferric ion increased the efficiency of degradation of aqueous phenol during PCO reaction, with concentration range of [F $e^{3+}$] = 0.1∼0.3 mM. Especially, in case of 0.2 mM of ferric ion, the reaction time for the complete destruction of aqueous phenol decreased to 1/3 of the control case (i.e. 150 min longrightarrow 50 min). However, ceric ion (C $e^{4+}$) was rarely effective with concentration range of [C $e^{4+}$] = 0.02 mM, but, still showed the possibility of electron acceptors.ptors.