The invention discloses a large movable water purifying system for an enclosed water area. The system which comprises a movable floating platform is characterized in that: the movable floating platform is provided with a water treatment device which comprises a filter unit, an adsorption unit, a micro-current electrolytic ion releasing unit, a micro-nano aeration unit and a water exchanging unit;the movable floating platform is also provided with a water quality information feedback device and a water purifying control device; and the signal output terminal of the water purifying control device is connected with the micro-current electrolytic ion releasing unit, the micro-nano aeration unit, the water exchanging unit and an instruction displaying unit. All units in the water treating device directly contact water of the water area, and in-situ treatment is carried out on polluted water depended on effects of the oxidation of active ions generated through filtration, adsorption and electrolysis, the interface activity of micro-nano bubbles and the like, so the slow flow of lakes, reservoirs, ponds, landscape water and the like or eutrophication and pollution problems of pesticides, organic matters and heavy metals of the enclosed water area can be effectively solved.