The invention discloses a device for improving water quality of laminated mixed oxygenated water. The device comprises an elevating cylinder, an aerating chamber, a gas storing chamber, an air releasing pipe, a guide plate, a perforated plate, a micro-pore aerator, a powerless automatic switching device and an anchoring pier, wherein the elevating cylinder is vertically arranged in water; the aerating chamber and the gas storing chamber are formed at the middle position of a reservoir; the micro-pore aerator is arranged at a position close to the bottom of the reservoir; a full-layer mixed oxygenation function and an isothermal layer mixed oxygenation function are integrated organically; and a telescopic cylinder for adjusting the height of the device is arranged between the aerating chamber and the micro-pore aerator, so that the stability of the entire device is improved. Through improvements on a multifunctional water pumping aerator, full-layer mixed oxygenation and isothermal layer mixed oxygenation are performed respectively by using the device for improving water quality of laminated mixed oxygenated water according to the water quality improving requirement, so that the problem of water quality pollution in the reservoir can be solved at lower energy consumption, and the aim of organically unifying two functions, the water quality improving benefit and the economic benefit is fulfilled.