Abstract: In order to solve the problem of large production and high toxicity of dye wastewater, which endangers human health and the ecosystem, iron-doped magnet-rich biochar (Fe-CCBC) was synthesized using corn cobs from agricultural waste as raw materials based on the technical idea of "turning waste into treasure". The efficacy and mechanism of Fe-CCBC-activated peroxymonosulfate (PMS) in the degradation of rhodamine B (Rh B) was studied. The physicochemical properties of Fe-CCBC were analyzed by various characterization methods. The results showed that Fe-CCBC-800 prepared at 800 ℃ had abundant pore structure and active sites, which could ensure the uniform distribution of Fe particles on the catalyst surface to the greatest extent, and it had excellent physicochemical properties and high catalytic activity. The Fe-CCBC-800/PMS system could remove Rh B up to 91% within 40 min. Moreover, the magnet-rich biochar was easier to recycle and reuse, and maintained a good catalytic effect in 5 cycles. The main reactive oxygen species in the Fe-CCBC-800/PMS system were \mathrmSO_4 ^- \cdot and ·OH, which were detected by reactive oxygen species quenching experiment and electron paramagnetic resonance (EPR) test. Fe²⁺, as an electron donor for redox reactions, participated in the activation process of PMS, and promoted the production of reactive oxygen species and the efficient degradation of Rh B. The Fe-CCBC-800/PMS system can realize the efficient treatment of Rh B, which provides a viable pathway for the utilization of agricultural waste and the rapid removal of dye contaminants.