The aim of this study was to treat of tannery wastewater with the chemical advanced oxidation using Fenton reagent. Advanced oxidation process was carried out using different doses of iron (Fe₂⁺) changes from 0.056 g Fe₂⁺/dm³ to 0.56 g Fe₂⁺/dm³ and H₂O₂ from 0.34 g/dm³ to 5.44 g/dm³. The wastewater samples were characterized for the concentration of chemical oxygen demand (COD), chromium, ammonia and pH, conductivity. The possibility of using the coagulation process using SAX 18 was also investigated. The efficiency of the applied processes was monitored by change mainly of chemical oxygen demand (COD). The maximum COD removal was 80% for Fenton’s oxidation process at pH 3.0, Fe₂⁺ (0.56 g Fe₂⁺/dm³) and H₂O₂ (4.08 g/dm³) and significantly higher than in the case of the coagulation process.