Disclosed is a starting up self testing method of an airway pressure sensor for an anesthesia machine. In a manual state a pressure value of the pressure sensor is detected and after the detection if the value is within an airway pressure measurement range but not within a sensor zero point voltage range the anesthesia machine is switched to a machine controlled state to detect the pressure value of the pressure sensor so that under the machine controlled state an airway is in communication with a bellows to enable gas possibly left in the airway to flow into the bellows to thus change the pressure value in the airway and hence if the current pressure value of the pressure sensor is reduced or directly in the sensor zero point voltage range the pressure sensor is valid. The self testing method enables a detection process to be more accurate and stable and can ensure the security and the reliability of a pressure sensor.
