To compare the anesthetic effects and the side effects of propofol combined with fentanyl, sufentanil and dezocine respectively in painless colonoscopy examination.?Methods?Four hundred patients who were planned to undergo painless colonoscopy examination were enrolled; and randomly divided into 4 groups: oxycodone group (group O), fentanyl group (group F), sufentanil group (group S) and dezocine group (group D), 100 cases per group. The patients were given one of the experimental drugs: 50.0?μg/kg, 0.5?μg/kg, 0.1?μg/kg and 100.0?μg/kg respectively according to the group assignment. After 5 minutes, they were slowly given 2?mg/kg propofol intravenously. SpO2, HR and MAP were recorded at the following time point: the induction of anesthesia (T0), enteroscopy into the anus (T1), the colonoscopy (T2), the colonoscopy (T3), the polyps (T4). The number of body movement, wake-up time, nausea and vomiting, dizziness and headache, abdominal pain and other adverse reactions, as well as the VAS score, were recorded after the patient recovered consciousness.?Results?MAP comparison: all patients MAP were significantly lower at T0 than T1 (P??0.05). On the contrary, the group D was significantly higher at T2, T3, T4 than T1 (P??0.05); However, D group was significantly higher at T2 than T1 (P??0.05), But the group D was significantly higher at T4 than T1 (P?