Bubble evolution induced overpotential for hydrogen production by water electrolysis is an important issue and the generated gas bubbles will cover the internal/external surface of the electrode. Herein, a flow-through electrode loaded with Co-based nanosheets is presented. Under the condition of flow-through mode, the catalysts can be adequately exposed because the generated bubbles can be timely removed from the catalyst surface. The overpotential can be reduced by about 100 mV for hydrogen evolution reaction (HER) and 57 mV for oxygen evolution reaction (OER) under the condition of 300 mA cm-2 and electrolyte flux of 339 m3 m-2 h-1. A novel electrolyzer assembled with flow-through electrode for hydrogen production by alkaline water electrolysis is conducted. The cell voltage can be decreased by 100 mV at 400 mA cm-2 at 6 M KOH, 338 K, and 1 atm, with the energy of 5 kWh Nm-3 required.