Generally, the depth of tracheal intubation is 20~22cm for adult females and 22~24cm for adult males, and it also needs to be judged according to the patient’s body size and so on. Tracheal intubation is mainly used for mechanical ventilation in the case of respiratory obstruction, as well as respiratory management during anesthesia, etc. The tracheal tube is usually inserted into the trachea through the mouth. Generally, the tracheal tube is inserted into the trachea through the mouth, up to 2cm below the vocal cords, and the thickness and depth of insertion of the catheter vary according to the height and weight of the patient. Women are generally smaller in size, so the depth of tracheal intubation is usually 20~22cm and a 7.0~8.0mm catheter is used. Men are generally larger, so the depth of tracheal intubation is usually 22~24cm, and a 7.5~8.5mm catheter is used. However, it is also necessary to judge specifically with the patient’s height and weight. The depth of intubation can refer to the above range, but also need to be adjusted according to the actual situation, inserted too deep, the catheter will enter the unilateral bronchial tube leading to one-lung ventilation, inserted too shallow easy to be dislodged, air leakage and so on.