Abstract: In this paper, SA@Fe₃O₄/L-met used sodium alginate (SA) as matrix precursor material, with magnetic composite gel balls obtained by immobilizing iron trioxide (Fe₃O₄) and L-methionine (L-met) by ion cross-linking. The influence of pH, dosage and initial concentration on Pb(Ⅱ) adsorption was explored. The results show that at pH=5, the dosage is 0.5 g·L⁻¹, the initial concentration is 20 mg·L⁻¹, SA@Fe₃O₄/L-met can achieve better adsorption efficiency for Pb(Ⅱ), and the maximum adsorption amount can reach 328.02 mg·g⁻¹, much larger than the adsorption capacity of SA@Fe₃O₄ and SA, 142.5 mg·g⁻¹ and 152.8 mg·g⁻¹. Studies on adsorption kinetics and thermodynamics show that the adsorption process is aligned with the second-order kinetic equation and Langmuir equation to a greater degree of fit, and the reaction process is a process of entropy increase and heat absorption. The structure and performance of the gel sphere were characterized by using SEM, XPS and VSM. It was found that the amino groups, carboxyl groups and hydroxyl groups in the gel ball participating in the reaction process, combining with Pb(Ⅱ), and there also exists ion exchange. After 5 times of desorption, the adsorption capacity of the material can still reach 210.5 mg·g⁻¹, which is an ideal environmentally friendly adsorbent.