The utility model relates to the technical field of zinc smelting, in particular to an overflowing device of an electrolytic tank for perfectly, effectively and sufficiently ionizing an electrolytic solution in a zinc smelting electrolytic tank for separating out elemental zinc. A spoiler is downwards arranged in a position from the top of the electrolytic tank with the distance of 150 mm away from the tank edge, an overflowing pipe is arranged in a position with the distance of 170 mm away from the electrolytic tank, and an overflowing box is arranged under the overflowing pipe arranged between the spoiler and the overflowing pipe in the electrolytic tank. The overflowing device can prevent the electrolytic solution from being fast and directly discharged from an overflowing opening, effectively slows down the liquid flowing speed, prolongs the circulation time of the liquid in the tank, and reaches the effect of natural circulation of the liquid, so the concentration of the liquid in the tank is uniform. At the same time, the effective height of the liquid level is ensured, the use area of a cathode plate and an anode plate is put into full play, and the yield of an electrolytic shop is improved. The overflowing device of the electrolytic tank can be widely used in metal electrolysis industry.