At present the usual method for tracheal intubation in clinic is that induction of anesthesia with sedatives and opioids with rapid onset of action, and then depolarizing relaxant or non-depolarizing muscular relaxant is used to facilitate tracheal intubation. A good muscular relaxant situation is supplied by use of muscle relaxant, however, its administration may be associated with significant side effects, and then the use of it is restricted on certain conditions, even more, produces some potential hidden troubles. With the broad clinical application of the new-style and superactive sedatives, inhalation anesthetics and opioids, more and more people show interest in endotracheal intubation without muscle relaxant, and the relative research is more and more widespread.