Fe₃O₄ magnetic nanoparticles were prepared by co-precipitation method, the surface of the magnetic particles was modified by SiO₂ and CM-β-CD, and Fe₃O₄-based magnetic nanomaterials (Fe₃O₄@SiO₂@CM-β-CD) with high adsorption properties were prepared. Single factor optimization experiments were carried out, and the physical and chemical properties of magnetic nanocomposites were characterized by TEM, EDS and BET. The adsorption behavior of Fe₃O₄@SiO₂@CM-β-CD on rare earth Er(Ⅲ) was investigated. The effects of adsorbent dosage, temperature and rotational speed on erbium removal rate were also investigated. The results show that when the dosage of SDBS is 1 g, the dosage of TEOS is 6 mL, the dosage of APTES is 1 mL, and the dosage of CM-β-CD is 0.5 g, the adsorption rate of Er(Ⅲ) can preferably reach more than 95%. When the contact time is 30 min, the initial concentration of Er(Ⅲ) is 10 mg/L, the initial pH is 4.5, the dosage of adsorbent is 30 mg, the temperature is 298 K, and the rotational speed is 150 r/min, the removal rate of Er(Ⅲ) is about 98%. After the adsorption of erbium, the nanomaterials were desorbed with 0.1 mol/L HNO₃ for 20 min, and the desorption efficiency of rare earth Er(Ⅲ) can be more than 87%. The adsorption mechanism of Fe₃O₄@SiO₂@CM-β-CD was investigated by XPS analysis. It is found that the adsorption of Fe₃O₄@SiO₂@CM-β-CD on Er(Ⅲ) is mainly by the inclusion of cyclodextrin cavity, supplemented by electrostatic adsorption and chemisorption. The results of this study can provide a new method for efficient recovery of rare earth elements with low concentration in aqueous solution.