Mn₂O₃ is a conventional catalyst that is applied in photothermal catalytic oxidation of toluene while regular anions like SO₄^2-, Cl^-, and NO₃^- from different Mn precursors are left in Mn₂O₃. When applied in toluene degradation, the declining activity of Mn₂O₃ is always observable because the residual anions block the Mn⁴⁺/Mn³⁺ active sites, shield the oxygen vacancies, and cube the production of active oxygen species (O₂^-, O^-). Herein, it is found that the residual SO₄^2-, Cl^-, and NO₃^- make Mn₂O₃ incapacitated in deeply oxidizing the intermediates and cutting off the reaction process, and their influence ranks in the order of SO₄^2->Cl^->NO₃^-. Compared with pristine Mn₂O₃, the drops in CO₂ conversion efficiency account for 11%, 60%, and 73%, respectively. Nevertheless, rinsing with water is an effective method to remove the residual anions, and the more the rinsing, the better the toluene mineralization degree. This work provides a profound cognition of the deactivation mechanism of SO₄^2-, Cl^-, and NO₃^- and points out an effective way to abate their negative effect for the first time.