A brand-new environmental-friendly magnetic cellulosic adsorbent MnFe2O4@Cel-g-p(AA-DMC) was synthesized by natural cellulose and easy-recovered magnetic particles MnFe2O4. Magnetic cellulose composites were characterized by SEM, TEM, XPS, XRD, BET, VSM, TGA and FTIR. The MnFe2O4NPs could activate the peroxymonosulfate (PMS) to produce various reactive oxygen species (ROS). Accordingly, magnetic cellulose composites can synergistic adsorption degradation of dyes from organic wastewater. The Congo red (CR) removal efficiency by MnFe2O4@Cel-g-p(AA-DMC) via PMS activated by MnFe2O4 reached a maximum of 96.9% and only 9% reduction after four adsorption-desorption cycles, indicating the stability and recoverability of adsorbent. It is worth noting that adsorbents can be quickly recovered from aqueous solution by external magnet owing to superior saturation magnetization (35.44 emu·g-1). A possible degradation mechanism of CR on the MnFe2O4@Cel-g-p(AA-DMC) composite was proposed. The results suggest that adsorbent display strong potential for the removal of CR dyes from organic wastewater.