A method was established to measure the separation factor of electrode material for electrolyzing alkaline aqueous solution. The (n1,g(D)/n2,g(H)) ratio of mixed gases from electrolysis was determined quantitatively with cryogenic gas chromatography (GC) when we electrolyzed alkaline aqueous solution that deuterium oxide and hydrogen oxide contain 30% of the potassium hydroxide. The (n1,l(D)/n2,l(H)) ratio of alkaline aqueous solution after electrolysis was tested quantitatively with the infrared spectroscopy, and then, the separation factor of different material was obtained according to the formula of separation factors. This method can be used to evaluate the separation ability of different electrode material for deuterium and hydrogen, which is helpful in the search of excellent electrode materials.