Most organic compounds are resistant to conven­tional chemical and biological treatments. For this reason, other methods are being studied as alter­natives to the biological and classical physico-chemical pro­cesses. In this study, advanced photochemical oxidation (APO) processes (UV, UV/H2O2, UV/H2O2/Fe(II), andUV/H2O2/Fe(III)) were investigated in lab-scale experiments for the degradation of phenol in an aqueous solution. A medium-pressure 300 watt (UV-C) mercury ultraviolet lamp was used as the radiation source and H2O2 30% as the oxidant. Phenol (initial concentration= 0.5 mmol/L) was selected as the model due to its high use and application. Some important parameters such as pH, H2O2 input concentration, iron catalyst concentration, the type of iron salt, and duration of UV radiation were studied based on the standard methods. The results showed that the Photo-Fenton process was the most effective treatment under acidic conditions producing a higher rate of phenol degradation over a very short radiation time. The process accelerated the oxidation rate by 4-5 times the rate of the UV/H2O2 process. The optimum conditions were obtained at a pH value of 3, with a molar ratio of 11.61 for H2O2/Phenol and molar ratios of 0.083 and 0.067for Iron/H2O2 in the UV/H2O2/Fe (II) and the UV/H2O2/Fe (III) systems, respectively.