A method device and respirator for controlling flow. Among them the method comprises: a two way flow controller triggers transferring a gas to a patient according to the detection conditions to provide the patient with a first breath through a breathing circuit (S202) when the first breath is finished a release unit is opened to release the gas in a dead space of the breathing circuit and a basal flow is transferred to the release unit (S204) then the two way flow controller again triggers transferring the gas to the patient to provide the patient with a second breath (S206). Said method and device enable the patient to breathe a fresh gas all the time when the patient has an aspiration action he/she can breathe the fresh gas thus reducing the breathing work of the patient.
