Abstract: Green synthesis of metallic nanoparticles is a promising field of research in recent years. It has been proved that the simple and cost-effective green synthesis process is environmentally friendly, stable and can be used for large-scale production. In this study, iron nanoparticles (ML-FeNPs) were synthesized using aqueous Medicago sativa L. extracts as both the reducing and capping agent. ML-FeNPs was analyzed by UV-Vis, XRD, SEM, TEM, FTIR and EDX techniques. The prepared ML-FeNPs are amorphous ellipsoid particle with particle size of 70-80 nm, and contain Fe₂O₃, Fe₃O₄, FeOOH and Fe⁰. In addition, ML-FeNPs are encapsulated by the organic groups of O—H, CH₂, C—H, C=C, C—N, C—O—C. The removal of U(Ⅵ) from aqueous solution by ML-FeNPs was also investigated. The optimum removal conditions are as follows: Initial U(Ⅵ) concentration of 10.000 0 mg/L, temperature of 25 ℃, reaction time of 90 min, pH of 6, dosing ratio of ML-FeNPs and U(Ⅵ) of 12.520 0 g/L. At this condition, the removal rate of U(Ⅵ) can reach 88.90% by ML-FeNPs. The removal of U(Ⅵ) mainly takes place in the surface of ML-FeNPs, the plausible mechanism for the removal of U(Ⅵ) using ML-FeNPs is the combined action of reduction, adsorption and complexation, and the removal of U(Ⅵ) is improved by the organic groups.