Ｏｂｊｅｃｔｉｖｅ　Exploring the effect and the optimal dosage of dexmedetomidine(Dex) during fiberoptic intubation in elder patients.　Methods　One hundred and twenty patients, ASA Ⅱ or Ⅲ, were randomly divided into four groups with the random number table (n=30): D1, D2, D3 and D4. Four groups received Dex loading dose of 0.2, 0.4, 0.6, 0.8 μg/kg respectively, all the dose were given in ten minutes, then followed with 0.2 μg·kg-1·h-1. MAP, HR, SpO2 maintenance. Observer′s assessment of alertness/sedation(OAA/S) score were recorded at baseline(T0), the time before intubation (T1), the time when bronchofiberscope reaching glottis(T2), 1 min after intubation (T3), 3 min after intubation (T4) and 10 min after intubation (T5). Intubation time, intubation tolerance, and satisfaction rate were also recorded.　Results　Compared with T0, OAA/S decreased significantly at T1-T5 in group D1, D2, D3 and D4(P<0.05), MAP decreased significantly in group D2, D3 and D4(P<0.05), HR increased significantly at T2 in group D1 and D2(P<0.05). Compared with D1, OAA/S, HR, MAP decreased significantly at T2-T5 in group D3 and D4(P<0.05). Compared with D2, OAA/S decreased significantly at T4-T5 in group D4. MAP and HR were decreased significantly at T2-T5 in group D4. The incubation success rates of 4 groups were 100%. The intubation time in group D2, D3 and D4 were significantly shorter than group D1(P<0.05). Group D2, D3 and D4 were significantly calmer and more cooperative during waking time for fiberoptic incubation, they were also more satisfied with the awake fiberoptic incubation than group D1(P<0.05).　Conclusions　Dex at a loading dose 0.4-0.6 μg/kg intravenously can be used safely in bronchofibroscopy for elder patients with less cardiovascular and respiratory depression and with more tolerance and satisfaction.