Ethylene propylene diene monomer (EPDM), known for its outstanding weatherability, aging resistance, waterproofing, and electrical insulation, is widely used as an insulating material in power cable accessories. However, its application is hindered by interfacial electric field distortion from dielectric mismatch, which increases dielectric breakdown risk, and by performance degradation under climatic, thermal, and mechanical stresses.In this work, methyl MQ silicone resin was incorporated into EPDM via melt blending, and the dielectric, thermal, and mechanical properties of the composites were systematically evaluated. Results show that MQ resin significantly enhanced EPDM performance: (1) Electrical performance: With 20 parts per hundred rubber (PHR) of MQ resin, the breakdown strength increased by 12.6%, reaching 130.6 kV/mm; (2) Thermal stability: Higher char residue at 600 °C indicated improved thermal resistance from physical barrier and free-radical scavenging effects; (3) Mechanical properties: Tensile strength peaked at 18.63 MPa at 20 PHR, while 30 PHR caused deterioration due to over-crosslinking; (4) Surface characteristics: Water contact angle increased from 105.0o to 109.9o, indicating better hydrophobicity. These results confirm methyl MQ silicone resin as an effective modifier for EPDM-based insulation in high-voltage cable applications.