By developing the mathematical model of a serial multi-stage reverse electrodialysis reactor (REDR) system for wastewater treatment, this paper numerically simulates the degradation process of azo dye (methyl orange) dyeing wastewater. The operation performances of the serial system with an anode and cathode synergetic degradative circulation mode are explored by numerical simulation. The influences of operation parameter variations on key performance indicators are investigated and discussed. Results indicate that the serial system can achieve excellent electricity conversion efficiency and degradative performance under an appropriate output current condition. A high initial MO concentration and electrode rinse solution (ERS) flowrate are helpful to improve the treatment performance of the system. A low concentrated solution (CS) concentration is beneficial for raising the electricity conversion efficiency and reducing the total energy consumption (TEC).