This study evaluated the performance of the photo-Fenton reaction when it was initiated using UV/H2O2 with steel waste and basic oxygen furnace slag (BOF slag), here called the UV/H2O2/BOF slag process, in order to decompose polyethylene glycol (PEG) in aqueous solution. The concentration of total organic carbon (TOC) was chosen as a mineralization index of the decomposition of PEG in the UV/H2O2/BOF slag process. A first-order kinetic model with respect to TOC was appropriately adopted to represent the mineralization of PEG in the UV/H2O2/BOF slag process. The experimental results obtained in this study suggest that dosages with 2.49 x 10(-4) mol/min-L H2O2 and 25 g/L BOF slag loading in a solution at pH = 2.5 with 120 mu W/cm(2) UV provided the optimal operation conditions for the mineralization of PEG yielding 79.5% mineralization efficiency after 90 min of reaction time.