Objective To investigate the effectiveness of different dose dexmedetomidine ( DEX) combined with video laryngoscopy during orotracheal Intubation for patients with spontaneous breathing. Methods A total of 87 emergency or intensive care unit ( ICU) patients with spontaneous breathing was in-cluded (age range:18 to 75 years).The patients were randomly divided into three groups with 29 cases each:midazolam combined with fentanyl group ( A) , low dose DEX group ( B) , and high dose DEX group (C).Mean arterial pressure (MAP),heart rate (HR), and SpO2 were detected before injecting different dosage drugs (T0), during intubation (T1),after intubation immediately (T2), at 3 min after intubation ( T3 ) .The amount of intubation time and side effects in each group were assessed.Results Compared to A group, the changes of hemodynamics in group B and C were more stable after injecting drugs.The doctors spend less time for intubation in group B and C.The rate of significant bradycardia in group C was higher than other groups.Conclusions If you can assess indications, doses and timings strictly, it was safety and availability to control intubation response in the patients with spontaneous breathing by injected of DEX.