Objective: The adsorption performance of the seed-shell biochar from Moringa oleifera prepared under different technological conditions on methylene blue was investigated in this study. Methods: The magnetic seed shelling biochar (Fe₃O₄-MOS) and modified seed shelling biochar (KOH-MOS) were prepared by ultrasonic-assisted K₂CO₃-Fe₃O₄ co-impregnation pyrolysis and KOH impregnation pyrolysis at 1 000 ℃, respectively. The physicochemical properties of the samples were characterized by XRD, SEM and FTIR. On this basis, the adsorption characteristics of the two kinds of biochar for methylene blue (MB) solution were determined by equilibrium adsorption method. Then the adsorption isotherm and kinetic model were used to fit the data to study the adsorption mechanism of biochar on MB. Results: It was found that under the experimental conditions, the adsorption efficiency of Fe₃O₄-MOS and KOH-MOS on MB was close to 100%, and the maximum adsorption capacity calculated by Langmuir model were 116.83 mg/g and 99.37 mg/g, respectively. Conclusion: The adsorption of MB by the two materials is a process of spontaneous endothermic entropy increase and chemical adsorption. Fe₃O₄-MOS showed good magnetic separation ability, while KOH-MOS showed good adsorption ability.