Abstract: The study was undertaken to examine the effect of H2O2/Fe2+ molar ratio as one of the important operating conditions on the performance of combined photo-Fenton-SBR process for treatment of recalcitrant (antibiotic) wastewater. The SBR was fed with photo-Fenton-treated antibiotic wastewater under five H2O2/Fe2+ molar ratio (10, 20, 50, 100 and 150). The results indicated that, as H2O2/Fe2+ molar ratio decreases (increase of Fe2+ concentration), BOD5/COD ratio of the photo-Fenton-treated effluent increases and SBR and overall efficiency increases. The SBR efficiency in terms of sCOD removal was observed to be very sensitive to BOD5/COD ratio below 0.40. It decreased from 69±1% at BOD5/COD ratio of 0.49±0.01 to 44±1% at 0.19±0.02. In this study, the best H2O2/Fe2+ molar ratio for treatment of the antibiotic wastewater was observed to equal 20. At photo-Fenton-SBR operating conditions (H2O2/Fe2+ molar ratio 20, H2O2/COD molar ratio 2.5, pH 3 and 30 min photo-Fenton irradiation time and 24 h hydraulic retention time in SBR), the combined photo-Fenton-SBR efficiency (overall) was 86% as sCOD and final sCOD was 56±2 mg L-1, which meets the requirements of the discharge standard.