Abstract: The large-scale use of antibiotics poses a significant threat to the natural environment and human health, so there is an urgent need to explore an efficient and green degradation method. In this study, Mn, P-doped corn stover biochar (Mn/P-C) was prepared for the degradation of norfloxacin (NOR) by activated permonosulfate (PMS). Compared with pure biochar BC, P-doped biochar (P-C), Mn/P-C has a larger defect structure and abundant surface oxygen-containing functional groups. Under the conditions of pH 2.84, PMS 3 mmol/L, and catalyst dosing 1 g/L, the NOR removal reached 94% within 80 min reaction time, and the degradation reaction rate of the system was 0.034 min⁻¹. The catalyst characterization, quenching experiments, and electron paramagnetic resonance (EPR) experiments demonstrated that, in the Mn/P-C-activated PMS system, the NOR was mainly removed via SO4^•− and O₂^•−radicals as well as the ¹O₂ non-radical pathway generated on the catalyst surface were degraded. In addition, Mn/P-C is effective in a wide pH range, has high reusability and stability, and does not cause secondary pollution to the environment due to its good magnetic properties. This study confirms that doping Mn and P can effectively improve the efficacy of biochar-activated PMS for NOR degradation, which provides a new idea for the optimization of carbon-based materials as well as their application in persulfate activation.