Abstract:【Objective】To compare the anesthetic effect and security of etomidate and propofol combined with midazolam and fentanyl anesthesia in the treatment of elderly patients with painless colonoscopy. 【Methods】 120 cases of patients undergoing colonoscopy and treatment were randomly divided into two groups: Etomidate composite group (E group, n =60) and Propofol composite group (P group, n =60). In both groups, patients were given midazolam 1mg and fentanyl 0.03~0.05 mg intravenously. Subsequently, P group patients were given propofol 1~1.5 mg/kg intravenously while E group patients were given Etomidate 0.1~0.3 mg/kg intravenously. After the patient slept and the lash reflex was abolished, we started the colonoscopy and treatment. The awakening time, adverse reactions and changes in patient’s SBP, DBP, HR and SpO2 were recorded at the following time points: before colonoscopy,colonoscopy instantly, 3 min, 5 min, 8 min, and 10 min after inserting the colonoscope. 【Results】 Both two groups of patients were satisfied with the anesthetic effect and successfully completed colonoscopy and treatment. The patient's awakening time in E group was (6.9±3.4) min, had no statistically significant difference than (6.1±2.9) min in the P group (P >0.05). Blood pressure and heart rate were decreased in all patients after anesthesia. In P group, there were 14 patients(23.3%) whose blood pressure were decreased by more than 20% of the basal blood pressure or lower than 90mmHg after anesthesia; while in E group only 5 patients(8.3%) happened. The two groups had statistically significant differences(P <0.01). There were 8 patients (13.3%) in P group with heart rate less than 55bpm after anesthesia, whereas in E group there were only 2 (3.3%) cases, which had a statistically significant difference compared with the P group(P <0.05). 11 patients(18.3%) in P group after anesthesia, whose SPO2 had a transient lower than 90%, however in E group only 2(3.3%) cases occurred. The two groups had statistically significant differences(P <0.01). Two patients in E group developed mild amyostasia, yet P group did not occur; 2 cases of patients in P group had symptoms of nausea and vomiting, while 4 cases occurred in E group. There was no statistically significant difference between the two groups (P >0.05). 【Conclusion】 Both etomidate and propofol combined with midazolam and fentanyl anesthesia in the treatment of elderly patients with painless colonoscopy can obtain a satisfactory anesthetic effect and be safe in clinical. However, in comparison, etomidate combined with midazolam and fentanyl anesthesia has smaller impact on the respiratory and circulatory, and more suitable for elderly patients with painless colonoscopy.