This a case report of airway obstruction due to mucous plug which occurred. as a complication of endotracheal intubation. This 16-year old patient was performed on endotracheal intubation for cardio-pulmonary resuscitation of cardiac arrest due to traume. He was comatous, tachypneic and increased pulse rate at 6 hours after intubation, then we found the uneven ventilation of both lung fields. We exchanged endotracheal tube after failure of suction and found airway obstruction due to mucous plug. After exchange of tube, suction of secretion and trachecstomy was performed. 3 days afterward, the patient was recovered from his poor pulmonary function, then transferred to the ward.