The invention discloses a nasal cavity channel diameter detection tube and relates to the field of medical consumables. The detection tube is provided with a detection tube body, wherein the front end of the detection tube body is provided with a guide part which is small in front and big in back, and the outer side of the detection tube body is provided with a length mark; the upper portion and the lower portion of the tube wall of the guide part are provided with through holes, a measuring air bag is arranged outside the portion, behind the guide part, of the detection tube body and connected with an inflator through an inflatable pipe via a one-way valve, and the inflator is provided with a scale which corresponds to the diameter of the measuring air bag and reflects the air injection amount; the detection tube body is connected with a breathing machine or an aspirator through an inlet and can provide an oxygen supply channel or suck secreta in the nasal cavity. The detection tube can achieve measurement of the passing diameter of the nasal cavity channel to provide a basis for choosing a proper cannula or catheter for a nasal trachea cannula and avoid aspiration by mistake caused by nasal mucosa damage and bleeding when an improper cannula or catheter is adopted.