The embodiment of the utility model discloses a device for preparing deuterium, which comprises an electric cathode container cylinder used for being connected with a negative electrode of a power supply; the diaphragm is arranged in the electric cathode container cylinder and is used for forming an anode region inner cavity and a cathode region inner cavity; the electric anode is used for being connected with a power supply anode and is arranged in the anode region cavity of the diaphragm; the activation source is used for activating the activity of D-O chemical bonds in the aqueous solution;after an aqueous solution is introduced along a water inlet, an activation source is input into an inner cavity of a cathode region at a preset angle, and a preset voltage is introduced into the device while the activity of a D-O chemical bond in the aqueous solution is activated, so that D + is electrolyzed out under the action of an electric field, and deuterium and deuterium-depleted water areobtained respectively. According to the utility model, deuterium in water is separated and concentrated in a lower-energy-consumption, cheaper-equipment and more environment-friendly manner, the operation is simple, complex equipment is not needed, and meanwhile, pollution-free deuterium-depleted water is produced.