The invention relates to a top-supply top-return purification ventilation system. The top-supply top-return purification ventilation system comprises air supply ports and air return ports, wherein theair supply ports are distributed in the top of a room to be used for delivering circulating air composed of treated return air and treated fresh air to the room; and the air return ports are distributed in the top of the room to be used for introducing return air from the room into the ventilation system for treatment. The air supply ports and the air return ports are provided with diffusion plates, so that the circulating air delivered by the air supply ports is jet flow while the return air introduced by the air return ports is converging flow. In addition, the relative positions of the airsupply ports and the air return ports as well as the orifice air speed of the air supply ports and the orifice air speed of the air return ports are adjusted to realize the effect that air supply jetflow regions of the circulating air delivered by the air supply ports and return air converging flow regions of the return air introduced by the air return ports do not overlap mutually in the spaceof the room. By means of the top-supply top-return purification ventilation system, the room space can be greatly saved while various air quality parameters are guaranteed.