Background: IoC2 (index of analgesic status monitor) is EEG based monitor, which detect the long-ranging electrical signals that are relayed to higher brain centers, which are activated by sensory neurons, knows as nociceptors caused by nociceptive stimuli (irritation, stress, tissue damage etc.). IoC2 monitoring could predict the deficit in analgesic component and occurrence of irritation in the brain center to nociceptive stimuli. According to IoC2 monitor suggesting that the suitable analgesic range for maintenance of analgesia is 30-50. The objective of the present study was to determine the effect of different doses of Sufentanil IV onIoC2 and hemodynamic changes to double lumen endobronchial intubation in patients undergoing thoracic surgery.　　Method: The study was approved by the department of anesthesiology (The First Affiliated Hospital Of Chongqing Medical University) including data from 93 patients scheduled for endobronchial intubation undergoing induction of anaesthesia with IV midazolam, propofol, vecuronium and different dose of sufentanil in different group. The patients are randomly allocated into three groups (n= 31, each group); those induction with Sufentanil 0.5μg/kg (Group I, n=31), sufentanil 0.6μg/kg (Group II, n= 31) and sufentanil 0.7μg/kg (Group III, n=31). Angel-6000 D multiparameter anaesthesia monitor used to see the IoC2 and another anesthesia monitor for hemodynamic response during intubation. Index of sedation status (IoC1), index of analgesic status (IoC2) and hemodynamic (HR, MAP) responses to noxious stimulation during endobronchial intubation was recorded.　　Result: The endobronchial intubation significantly increased IoC1, IoC2 and MAP values in all three groups (P＜0.05). Following 3 minutes and 5 minutes after intubation the Index of sedation status (IoC1), index of analgesic status (IoC2) and hemodynamic response (MAP) significantly changed compared between three groups. There were no significant differences in HR in different time periods in all three groups (P＞0.05). The Group III had significantly lower values of IoC1, IoC2 and MAP than did the Group I at before intubation (P＜0.05) but there was not the significant change in Group II.　　Conclusion:We compared the ability of different dose of sufentanil to prevent stress irritation caused by double lumen endobronchial intubation, which is assessed by IoC2 monitor. Our study result showed that, IoC2 range to be found exceed from the maintenance analgesia range (30-49) after endobronchial intubation with the dose of sufentanil 0.5μg/kg while with the dose of sufentanil 0.6 μg/kg and 0.7 μg/kg IoC2 found to be with in the desirable range which is 30-49. According to IoC2 range (30-49), Sufentanil 0.6 mcg/kg and 0.7 mcg/kg are more effective in controlling the stress irritation and hemodynamic changes than sufentanil 0.5mcg/kg during double lumen endobronchial intubation. So, Index of analgesic status (IoC2) can guide the appropriate dose of sufentanil as it monitors depth of analgesia to distinguish a deficit in opioids.