Carbon dioxide decomposition in a micro-slit sustained glow discharge reactor operated at low pressure of 8Torr was studied experimentally. A specially designed reactor with a micro-slit configuration, combined with a third electrode that allows the extraction of electrons from the micro-slit discharge, was used to extend the glow discharge volume of the micro-slit discharge. It is found that, with the increase of the applied voltage of the third electrode, both the conversion fraction and energy efficiency of CO2 decomposition increase. The three-electrode structure was also extended to parallel operation to investigate the effects of applied voltage, flow rate, and number of parallel units on the conversion fraction and energy efficiency of CO2 decomposition. A maximum energy efficiency of 7.2% was achieved at a flow rate of 30ml/min and power of 2.1W for a single discharge unit, while for three discharges units connected in parallel, the maximum conversion fraction was 26.2% at a flow rate of 2ml/min and power of 6.6W. The results demonstrate the feasibility of parallel operation of the three-electrode micro-slit discharges, and increasing the number of parallel discharges increases both energy efficiency and conversion fraction at high flow rates. A better understanding of the physical and chemical kinetic processes will lead to optimization of future reactors to improve conversion and energy efficiency.