Abstract: In order to solve the problem that Fe₃O₄ nanoparticles were easy to be corroded and agglomerated, it was decided to functionalize it. Magnetic nano-Fe₃O₄ particles were prepared under ultrasonic irradiation, then 2-diaminobenzenesulfonic acid (SP) and m-phenylenediamine (mPD) monomers were selected as introduction agents to prepare metal matrix composites Fe₃O₄-mPD/SP(95∶5), which were rich in amino, sulfonic acid and imine active functional groups, and nanocomposites were characterized by FTIR, TEM, XRD and other methods. The characterized results show that the magnetic nanocomposites prepared by ultrasonic strengthening method have the characteristics of good stability, high reaction activity, small particle size and larger specific surface area. The adsorption properties of Pb(II) by Fe₃O₄-mPD/SP were investigated which showed that the molar percentage of SP and mPD, reaction temperature, sorts of competitive cations and the pH value of solution all had effect on the adsorption of Pb(II). The adsorption isotherm conforms to the Freundlich model, and the adsorption of Pb(II) is a spontaneous process, Gibbs free energy ∆G⁰<0. It is found that the adsorption behavior of Pb(II) on nanocomposites can be well described by quasi secondary dynamics equation, kinetic constant k₂=3.61×10⁻³ g·mg⁻¹·min⁻¹, equilibrium adsorption capacity q_e=63.297 mg·g⁻¹. It is speculated that the adsorption mechanism of this adsorbent includes ion exchange, complex adsorption and electrostatic adsorption.