The structure and properties of zinc-neutralized sulfonated EPDM (Zn-SEPDM) plasticized with modified glyptal resin (GR) were studied through mechanical property tests, capillary rheometry, differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). The results show that GR can considerably reduce the glass transition temperature as well as the apparent melt viscosity of Zn-SEPDM, and that the mechanical properties of Zn-SEPDM plasticized with GR are much better than those of Zn-SEPDM plasticized with traditionally used zinc stearate (ZnSt).