The fresh air dehumidification host is connected to each room indoors, via the pipeline, to dehumidify or ventilate according to the needs in different seasons, where the central dehumidification and ventilation, as well as automatic dehumidification according to the humidity value set by the customer without manual guard, are available. Meanwhile, it has the function of purifying air while circulating and dehumidifying, thus keeping the air in the living space fresh and the humidity proper.