A three-dimensional electro-peroxone (3D-EP) system achieved efficient degradation of high salinity organic wastewater and showed significant implications for potential application. Herein, an MgMn-granule-activated carbon (GAC) particle electrode was developed through impregnation calcination and applied in multipollutant removal. The integration of electrolysis, ozone application, and MgMn-GAC in the 3D-EP system manifested strong synergy, leading to successful elimination of all phenol within 30 min due to ample hydroxyl radical production. The energy consumption of MgMn-GAC was 1.86 kWh·m−3 and the specific energy consumption was 0.033 kWh·g−1 COD, exhibiting high electrical energy utilization efficiency under low applied current and low O3 exposure conditions. After six consecutive reaction experiments, COD removal reached 95.6 %, demonstrating remarkable catalytic activity and cycling stability. The study findings indicate that this material could be used as a low-cost particle electrode for practical wastewater treatment.