Phosphate residue is a kind of hazardous solid waste and if not properly disposed of,could cause serious environmental contaminations.The abundant iron salt available in phosphate residue can be used to prepare photo-Fenton catalytic reagent for wastewater treatment.In this study,the phosphate residue was effectively purified by a hydrothermal recrystalliza-tion method,reaching an iron phosphate purity of 94.2％.The particles of iron phosphate were further processed with ball milling with their average size reduced from 19.4 to 1.6 μm.By hydROthermal crystallization of iron phosphate and thermal decomposition of oxalate precursor,porous iron hydroxy phosphate was prepared.The modified porous iron hydroxy phosphate (m-PIHP) of higher surface area with iron oxalate on its surface can degrade 98.87％ of Rhodamine B in 15 min.Cyclic experiment showed that the catalyst still had a good catalytic activity after six cycles (＞40％).The X-ray photoelectron spectroscopy results showed that the iron oxalate complex on the catalyst surface decomposed to produce fer-rous ions and accelerated the rate of ·OH production.The current work demonstrated that the m-PIHP synthesized from phosphate residue and modified with iron oxalate can be used as an effective dye wastewater treatment agent.