To resource utilization of the spent cation exchange resin, the carbonized resin with Fe doping (Fe₃O₄@CR) was prepared to activate persulfate (PS) for the degradation of oxytetracycline (OTC). Fe₃O₄@CR exhibited high catalytic potential for the degradation of OTC with relatively low activation energy (E_a = 28.86 kJ/mol). In the Fe₃O₄@CR/PS system, 76.4% of the OTC was removed under the conditions ([PS]: 0.15 g/L, [Fe₃O₄@CR]: 0.3 g/L, T: 25ºC). Fe₃O₄@CR could work effectively for activating PS to degrade OTC in the pH range of 3.0-7.0. The free radical quenching experiments and electron paramagnetic resonance (EPR) analysis showed that ^•OH and SO₄^•- were the main radicals for the degradation of OTC. The conversion between Fe³⁺ and Fe²⁺ accelerated the degradation of OTC by generating ^•OH and SO₄^•-. The possible degradation pathways were proposed. The OTC was mineralized to smaller molecules, such as C₁₄H₁₀O₃ and C₇H₁₁O. This study offers a new perspective on waste resin recycling and water purification.