A DC electromagnetic pump with a rectangular channel was optimally designed and fabricated for studying the reaction between liquid sodium and carbon dioxide (CO2) gas in a sodium fast reactor. Heat exchange using CO2 gas has recently been proposed for the secondary sodium loop of the sodium fast reactor being developed in Korea because of the strong chemical reaction between liquid sodium and water. A DC conduction-type electromagnetic pump with a rectangular channel was selected to circulate liquid sodium in the experimental test loop for the sodium-CO2 reaction. Electromagnetic force, which was generated by the Lorentz force of an electrical equivalent circuit, was used to drive the liquid sodium. The developed pressure of the pump was investigated using optimization of the geometrical and electromagnetic variables of the pump considering Lorentz force, electromotive force, and hydraulic loss in the narrow channel of the pump. The characteristics of the developed pressure were studied with respect to the flow rate, and the pump was fabricated using the optimized design specifications. The distributions of current and magnetic flux density in the narrow channel were calculated for the fabricated DC electromagnetic pump with a flow rate of 3 L/min and developed pressure of 0.05 bar, operated at a temperature of 300 °C. A comparative analysis of the performance of the designed pump was investigated by considering the fringe effects and Lorentz force using both the equivalent circuit method and numerical analysis.