Abstract: The Fe₃O₄ is prepared by coprecipitation under the alkaline conditions, and then the Fe₃O₄ composite materials (Fe₃O₄-SiO₂-NH₂) are synthesized with tetraethyl orthosilicate and diethylenetriamine as the main raw materials. FT-IR, VSM and SEM are employed to characterize their structures, and the adsorption performance of Cd²⁺ by Fe₃O₄-SiO₂-NH₂ composites are studied. The results showed that under the conditions of T=55℃, contact time of 60 min, an initial Cd²⁺ concentration of 100 mg·L^-1 and an amount of Fe₃O₄-SiO₂-NH₂ composite of 0.1 g, the adsorbent capacity of the composite for Cd²⁺ is found to be 71.4 mg·g^-1. The adsorption kinetic behavior of Fe₃O₄-SiO₂-NH₂ composites for Cd²⁺ is consistent with the quasi second-order kinetic and thermodynamics is suitable to be described by Langmuir isothermal adsorption model. The removal rate of Cd²⁺ is still above 70% after five times regeneration of Fe₃O₄-SiO₂-NH₂ composite materials.