The invention relates to a liquid level control device for additives. The liquid level control device comprises an additive circulating box, an additive storage tank, a stirrer and a computer control chamber. A liquid level sensor is arranged in the additive circulating box, an overflowing pipe is arranged on one side of the additive circulating box, and a water flow sensor is arranged in the overflowing pipe; the additive storage tank is connected with the additive circulating box through a pipeline and a high-pressure pump, and the overflowing pipe enables the additive circulating box and the additive storage tank to be communicated; the high-pressure pump, the liquid level sensor and the water flow sensor are all electrically connected with the computer control chamber. By arranging the liquid level sensor, the overflowing pipe and the water flow sensor, the liquid level in the additive circulating box is monitored and controlled dually, the height of the liquid level in the additive circulating box is effectively controlled, and resource waste and environment pollution caused by overflowing of the additives are avoided.