Segmental resection of the trachea is the last resort for the treatment of tracheal stenosis and tracheal tumors, and it is also the best means for the treatment of some complex cases. The structure of the human trachea resembles a threaded tube, which can bend back and forth along the longitudinal axis, or stretch up and down along the longitudinal axis in length, or rotate and twist left and right along the longitudinal axis. It is supported by dozens of horseshoe-shaped cartilage rings arranged parallel up and down to ensure that the trachea does not become excessively narrow or bulging in the lumen during breathing, whether calm or forceful, the negative pressure of inspiration and the positive pressure of exhalation, and under normal circumstances, the gas exchange function that meets sufficient human needs is guaranteed for life. However, if the trachea is softened, for example, multiple tracheal cartilage rings are broken; or, for example, the cartilage rings are not sufficiently tough and supportive due to prolonged pressure or disease. All of them can seriously affect the stability of the tracheal lumen, causing severe respiratory distress and even death by asphyxiation. In addition to this, in recent years, we have found that there is another condition. The human trachea is usually only 10~11cm in length, and if 1~2cm is removed, it is easy to restore the normal length due to the inherent stretching function of the trachea, and there is no major impact on the respiratory function. However, if the trachea is resected “too long”, there is a possibility of a catastrophic situation that is least expected, i.e., exceeding the limit of tracheal stretch, and even with the application of various documented release methods, it will not be possible to complete a one-stage anastomosis, which would be a catastrophe! The patient and the surgeon would not be able to get off the operating table! If it is still possible to barely anastomose DD clinically mostly, sometimes it is necessary to use laryngeal release, sometimes it is necessary to cut the inferior pulmonary ligament, sometimes it is even necessary to sacrifice one lung, and after surgery, the patient’s chin has to be sutured to the front of the sternum with thick sutures to ensure the head is flexed forward, so that the trachea is less stretched and smooth healing is ensured. Once an anastomotic fistula occurs, the mortality rate is high. This is currently the best method available for large tracheal resection and the best result that can be obtained. The Grollo study showed that the longest trachea that can be resected is 6.8 cm, which is clinically accepted to be about half the length of the trachea, or about 6 cm. Because the trachea is stretchy, the resected specimen will be shortened, as will the two severed ends. Therefore, the measurement of the length of the resected tracheal specimen will be a little shorter than the length on the living body, and the measurement of the distance between the two broken ends will be longer than the actual length of the resected trachea, and the error will be a little larger once the neck is tilted forward or backward. So the clinical proposed so-called resection of a few centimeters are not very accurate. And Grillo’s experiment is an ex vivo specimen experiment to determine the longest resection distance without splitting the anastomosis under the same weight of tension. Therefore, it can only be used as a reference. It is not clinically possible to cut to the limit length proposed by his experiment, because then, it is likely to be impossible to anastomose, or to anastomose safely and reliably, to achieve an anastomosis that ensures optimal healing, or even to become a disaster on the operating table. Therefore, the clinical ability to remove 4-6 cm is already the maximum capacity of the few specialists who can complete trachelectomy. The authors have completed nearly 50 cases of trachelectomy anastomoses, but 5 cases of 5-6 cm resection. According to most of our literature reports, more than 4 cm can be considered as a large trachelectomy. This corresponds to more than one-third of the total length of the trachea. There are few serious complications that can be found in the literature. Most of the cases were not major resections, which is probably one of the main reasons why there were not many serious complications. The longest case resected by the authors was 8 cm, but of course it was not a one-stage anastomosis, but the Zhao’s artificial trachea technique was applied. The first stage anastomosis of 5~5.5cm healed in one stage. However, the 6-cm case died 9 days after surgery due to high respiratory distress and secondary intubation resulting in anastomotic dehiscence, and died a month later from severe mediastinal infection. Therefore, the authors’ limited experience can only say that 6 cm is the limit of unsafe.