Hydrogen economy is crucial for our society, and the efficient storage of hydrogen is a key step. Formic acid is a relatively ideal medium for hydrogen storage. The hydrogenation of CO₂ to formic acid is a thermodynamically limited reaction; thus, the continuous production of formic acid from CO₂ effectively is very interesting. Herein, we report a method of continuous-flow formic acid production via the hydrogenation of carbon dioxide using water as the solvent without any base, and the concentration of formic acid by electrodialysis offline and online was tested. The TON of the reaction could reach 35 000, and 2.5 mol L⁻¹ formic acid aqueous solution was obtained after concentrating by electrodialysis.