Abstract: In order to prepare the shielding materials of the rare-earth type which has light weight and unleaded innocuity, maleic acid samarium complex (Sm-MA) was synthesized by Sm₂O₃ and maleic anhydride (MA) through precipitation method firstly. Then, Sm-MA was used to modify ethylene propylene diene monomer rubber (EPDM), and Sm-MA/EPDM composites were prepared. Finally, the Sm-MA was tested by TG, FTIR, SEM and XRD, as well as the mechanical properties, morphology and shielding property (X-ray energy was 59.3 keV) of Sm-MA/EPDM composites were characterized respectively. The TG results show that the thermal decomposition mass loss of Sm-MA is closed to end at about 850℃, the total mass loss ratio of Sm-MA is 43.7%, and the content of Sm in Sm-MA (47.6wt%) which is calculated by experimental data is approximately consistent with the theoretical calculated value 46.8wt%. The FTIR spectra show that the characteristics absorption peak of -COOH in MA disappears after the formation of complex, as well as symmetrical and antisymmetric stretching vibration absorption peaks of carboxylic acid appear, which means Sm³⁺and MA bonded. Mechanical property and shielding property test results show that Sm-MA can reinforce both of the mechanical properties and shielding property of EPDM significantly. When the mass ratio of Sm-MA to EPDM is 60:100, the properties of Sm-MA/EPDM composites reach the best, the tensile strength is 18.3 MPa, the reinforced ratio reaches 33.6% and the shielding ratio reaches 77.1%. The conclusions obtained indicate that the addition of innocuity metal complex can not only improve the properties of composites, but also enhances the compatibility with environment.