Abstract: ob＜x＞jective To observe the therapeutic effect of dizocine plus propofol on respiratory depression in obese patients undergoing painless colonoscopy. Methods A total of 92 obese patients were randomly divided into two groups: dizocine group (Group D) and control group (Group C). They were randomly intravenous injected 0.05 mg/kg dizocine (diluted to 5 ml) or 5 ml normal saline, and then 2 mg/kg propofol was intravenous injected 5 minutes later. Propofol ( 4 mg· kg-1· h-1）was used for anesthesia maintenance. The main outcome measure was the number of times SpO2 decreased. T he secondary outcome measures were the number of apnea episodes, the time of the first hypoxia episode and the total consumption of propofol. At the same time, consciousness loss time; awakening time; Ramsay score; duration of post-anesthesia care unit (PACU) stay ; VAS score ; endoscopist satisfaction ; patient satisfaction and adverse events were also observed. Results Demographic characteristics between the two groups were comparable. Compared with group C, the number of apnea episodes and oxygen-desaturation episodes in group D were decreased, the amount of propofol used was reduced, the time of loss of consciousness and the time of awakening were shortened, stayed in PACU for a short time, and the satisfaction of endoscopists and patients was increased, the difference was statistically significant (P <0.05 or P <0.01). Kaplan-Meier curves showed that the median time of the first time of hypoxia attack in group D (71.5 seconds) was longer than that in group C (53.5 seconds), the difference was statistically significant ( P <0.01). There was no significant difference in Ramsay score and adverse event rate between the two groups (P >0.05). Conclusion Dezocine plus propofol for painless colonoscopy can reduce the frequency of SpO 2 decline and apnea in obese patients, and improve the safety of anesthesia.