The metals ions of wastewater including Cu(Ⅱ),Mn(Ⅱ),Fe(Ⅱ), Fe(Ⅲ) and Al(Ⅲ) were selected as representatives, and the experiments were carried out to assess the effects of metal ions on TNT-removal by O₃/H₂O₂ in the wastewater. The experimental results showed that effects of metal ion on the TNT degradation with O₃/H₂O₂ depend on the metal types and their concentrations in the wastewater. Cu²⁺ suppresses the degradation. Mn²⁺with a low concentration enhances the degradation, but suppresses the degradation with high concentration. The effects of Fe²⁺ and Fe³⁺ are opposite to that of Mn²⁺, and they enhance the degradation with low concentration and inhibit it with high concentration. Al³⁺ has a small potential to improve the degradation. Cu(Ⅱ), Fe(Ⅱ), Fe(Ⅲ) inhibit the TNT-degradation by O₃/H₂O₂ by blocking forming of hydroxyl radicals, and Mn(Ⅱ) does that by shorting the hydroxyl radical age.