The effect of a uniform magnetic field on the water electrolysis reaction in 4.46 mol/L KOH solution was investigated. A set of magnets is used to set up the uniform field which is parallel to the electrode surfaces. Two parallel platinum sheets (4 x 4 mm) embedded into glass surfaces are used as cathode and anode. Experiment results show that when the direction of Lorentz force is opposite to gravity, the force plays positive effect on the decrease of cell voltage all the time within experiment current range. If the orientation of Lorentz force is inversed, i.e. same to gravity, the force is no longer useful to decrease the cell voltage with the current density of 1.5 A/cm(2) below. Furthermore, Euler-Euler model is used to simulate the gas generation, electrolyte flow and gas distribution. The simulation results show that if Lorentz force is in the opposite direction of gravity, it helps gaseous product outflow directly. On the contrary, if the force is in the direction of gravity, it induces a vortex around anode and cathode which is against of expelling gas off the electrodes especially in the case of lower current density.