Most of the calcium peroxide (CaO2) based Fenton oxidation studies focus on the individual pollutant degradation. In this study, the simultaneous oxidation of benzene, toluene, ethylbenzene, and xylene (denoted as BTEX) by CaO2 based Fenton system was demonstrated. It was observed that BTEX removal increased with increasing molar ratios of CaO2/Fe(II)/BTEX. In the case of CaO2/Fe(II)/BTEX molar ratio of 5/5/1, BTEX removal were 35% in the ultrapure water and 15% in the actual groundwater. In the case of CaO2/Fe(II)/BTEX molar ratio of 40/40/1, BTEX removal were elevated to 98% in the ultrapure water and 88% in the actual groundwater. Chelating Fe(II) agents, such as citric acid (CA), oxalic acid (OA), and glutamic acid (GA), significantly enhanced the destruction of BTEX. When the molar ratio of Fe(II)/CA, Fe(II)/GA, and Fe(II)/OA was 10/20 while fixing CaO2/Fe(II)/BTEX molar ratio of 10/10/1, the enhancements in BTEX removal were 60%, 32%, and 72%, respectively. In terms of BTEX removal, OA chelated Fe(II) was demonstrated to be most effective in the CaO2/Fe(II)/BTEX system. Based on TOC analysis, the transformation effect was confirmed. The transformation products of BTEX were determined and oxidation pathways were proposed, in which HO center dot was mostly responsible to the parent compounds mineralization.