Abstract: A plant-based electrochemical device for ecological restoration of a polluted river or lake and a using method thereof are provided. The plant-based electrochemical device includes a sediment, where a plurality of first electrodes are provided in the sediment, the plurality of first electrodes each include a plurality of staggered cylinders, an outer side of each of the plurality of cylinders is provided with an electrically-conductive layer, and the electrically-conductive layer is electrically connected to an external power supply; a plurality of upright posts are symmetrically fixed in the sediment, the plurality of upright posts are fixedly connected to a second electrode through a fixing mechanism, and the second electrode is located at a water surface and is electrically connected to the external power supply; and a plurality of ecological landscape floating islands are provided on the water surface.