In this study, the degradation of 2-naphthalenesulfonic acid (2-NSA) was investigated by homogeneous Fenton oxidation. The influence of reaction time, amounts of H2O2, ratio of H2O2/FeSO4, solution pH and concentration of Na2SO4 was investigated on degradation of 2-NSA by homogeneous Fenton oxidation. The optimum conditions were obtained to be 120 min of reaction time, H2O2/FeSO4 of 10 solution pH of 3 and H2O2 amount of 41.6 mg/L for a 2-NSA concentration of 50 mg/L with a COD removal of 96.0 %.