Abstract: he magnetic separation and recovery of MnFe2O4@biochar (MBC) was prepared from agricultural waste peanut shell by high-temperature calcination and co-precipitation method, and the morphology and structure of MBC were characterized and analyzed. Rhodamine B(RhB) was degraded by MBC activated sodium persulfate (SPS).The effects of MBC dosage, SPS concentration, initial pH value of solution and co-existing ions on RhB degradation rate were investigated, and the reuse performance of MBC was also investigated. The results show that when the initial concentration of RhB is 10 mg/L, the initial pH value of the solution is 6.50, the MBC dosage is 0.4 g/L, and the SPS concentration is 2.0 mmol/L, the degradation rate of RhB reaches 93.2% in 120 minutes. Its degradation rate increases with the increase of MBC dosage and SPS concentration, and has a higher degradation rate at lower pH values (1-7). Humic acid, Cl^–, and HCO₃^– have a certain inhibitory effect on the degradation of RhB. The saturation magnetization of MBC is 5.28 emu/g, indicating that it is easy to magnetic recovery.MBC has good magnetism and stability, and after three cycles, the RhB degradation rate can still reach 73.8%. As a heterogeneous magnetic catalyst, the MBC prepared in this study could persistently activate SPS and achieve the degradation of RhB.