The invention discloses a purification system for a respiratory ward. The purification system comprises a filter and sterilization host, an outdoor air inlet switching assembly, a hanging rail assembly, a breathing assembly, a filter element, a sterilization cavity, an indoor air inlet, an outdoor air inlet, an output air port, an input air port, a switching main pipe, a cam with a shaft, a wall penetration pipe, a breathing mask, an inhalation hose, an exhalation hose, an inhalation transfer valve, an exhalation transfer valve, an output tube, a check valve body, a check valve joint, and a rubber inner core; the filter and sterilization host is put in the designated position of the respiratory ward, round holes are formed in the corresponding position on the wall, and the input of outdoorfresh air is realized through the outdoor air inlet switching assembly; the hanging rail assembly is mounted on the roof of the respiratory ward; and an inhalation joint and an exhalation joint of the breathing mask are respectively inserted in the output air port and the input air port of the filter and sterilization host through the hoses, inputting external air to a pneumonia patient after filtering and sterilization is realized, and the sterilization of the exhaled air of the pneumonia patient is also realized, so that the cross-infection in the respiratory ward is prevented.