Objective To compare the effects of the equivalent analgesic doses of sufentanil, fentanyl and dizosin on index of consciousness (IoC) and their adverse reactions. Methods Eighty patients undergoing painless gastroenteroscopy, aged 18～60 years, ASA grade Ⅰ to Ⅱ, were selected. The patients were randomly divided into control group (group C) , sufentanil group (group S) , fentanyl group (group F) , and dizosin group (group D) , with 20 cases in each group. Sufentanil 0.1～0.2 μg/kg, fentanyl 1～2μg/kg and dizocine 0.1～0.2 mg/kg were intravenously injected in group S, F and D respectively. Group C was given saline of equal volume, and then propofol 2～2.5 mg/kg was intravenously injected until consciousness disappeared.Intravenous infusion of propofol50～100 g/ (kg · min) maintained anesthesia. Heart rate, blood pressure, IoC and perioperative adverse events were recorded. Results There was no significant difference in operative time and recovery time among the 4 groups (P> 0.05). Compared with those in group C, the values of IoC at T2, TS, T4 and T5 in group S and F increased significantly (P < 0.05) , and the correlation coefficient between OAA/S and IoC was 0.872 (P < 0.05). Compared with that in group C, the incidence of nausea and vomiting was higher in group D, and the incidence of injection pain was significantly lower in group S, F and D (P < 0.05). Conclusion Compared with propofol alone, opioids used in painless gastrointestinal endoscopy anesthesia lead to loss of consciousness and increase of IoC value at recovery time, but have no significant effect on recovery time.