The invention discloses a three-phase overflow high-efficient oxygen-supplementing wetland system, and solves the problems of poor reoxygenation effect, high energy consumption, low removal efficiencyof COD (Chemical Oxygen Demand) and nitrogen and phosphorus, easiness for occurring short flow phenomenon, organic sewage blocking and the like existed in existing wetland. A wetland bed is divided into a central embedding area and a peripheral overflow area, so that the central embedding area can provide a three-phase coexistence environment of solid, liquid and gas for a to-be-treated water body, so that efficient oxygen supply is realized, and gas mass-transfer efficiency is also enhanced. The three-phase overflow high-efficient oxygen-supplementing wetland system is characterized by comprising the wetland bed, wherein a central baffle plate for dividing the wetland bed into the central embedding area and the peripheral overflow area is arranged in the middle of the wetland bed, and the filler height of the central embedding area is higher than that of the peripheral overflow area, so that the central embedding area is in the three-phase coexistence environment of solid, liquid andgas.