The invention relates to a water heater and a control method thereof. Specifically, the invention provides a water heater, comprising an inner container used to store water and an electrochemistry descaling device. Especially, the electrochemistry descaling device comprises a first electrode sheet, a second electrode sheet, and a spacing layer. The first electrode sheet, the spacing layer, and the second electrode sheet are overlaid in sequence, and are winded for a circle along the inner wall of the inner container to form a cylinder. In addition, the invention also provides a control method for the water heater. The water heater and the control method obviously improve descaling area of the electrochemistry descaling device because of the special structure and the installation position of the electrochemistry descaling device, and prevent or greatly slow down scale formation on the heating pipe and the inner wall of the inner container of the water heater.