The endocrine disrupter Atrazine was oxidized by O3/H2O2 system and the products were analyzed to assess the degradation efficiency of Atrazine. When it's initial content was 2 mg/L and O3 dosage was 7.5 mg/L, Atrazine was removed about 27.2% after 5 minutes. Under the same condition, H2O2/O3 molar ratio was 0.75, Atrazine maximum removal rate reached 96.5%, which suggested that Atrazine could be degraded by O3/H2O2 system effectively. Ion Chromatography (IC) analysis showed that concentrations of chloride and nitrate ions were increasing along with the Atrazine content decreasing. Gas Chromatography-Mass spectrometry (GC-MS) and Liquid Chromatography-Mass spectrometry chromatograms (LC-MS) analyzing illuminated the existence of de-ethyl-atrazine, de-isopropyl-atrazine and de-chloro-atrazine, which indicated the Atrazine could not be destroyed completely by O3/H2O2 system. Consequently, it should be combined with GAC (Granular Activated Carbon) or other techniques while used as primary treatment unit or emergency measure.