Objective To assess the safety and comfort of colonoscopy with carbon dioxide(CO2) insufflation in elderly people. Methods This was a randomized controlled double-blind study. Totally 110 consecutive elderly participants undergoing colonoscopy were randomized into air insufflation group(n = 55) and CO2 insufflation group(n = 55). Patients’ experiences of abdo minal pain and bloat were registered using Visual Analog Scale (VAS). The degrees of pneumatosis in the intestinal canal were recorded by the X-ray exam. Transcutaneous partial CO2 pressure was continuously measured with a capnograph as a safety parameter. Above parameters were compared between air insufflation and CO2 insufflation group. Results VAS scores and pneumatosis scores in CO2 group were significantly lower than those in air group [(7.0±4.9) vs (9.0±3.7) min; P＜0.05] during and after examination. The questionnaire survey of abdominal pain and bloat at different time points (5, 10, 15, 20 min after colonoscopy) showed that the questionnaire score in CO2 group were significantly lower than that in air group [5min: (15.4±2.1) vs (63.5±13.5); 10min: (5.1±1.3) vs (60.3±10.9); 15min: (0.5±0.7) vs (58.6±11.6); 20min: (0.0±0.7) vs (50.4±8.2); P＜0.01]. The intestinal dilatation scores were significantly lower in CO2 group compared with that in air group [(1.2±0.5) vs (3.6±0.9); P＜0.05]. No significant changes of end-tidal CO2 pressure were found between CO2 and air groups. Conclusion Compared with air insufflation, colonoscopy with CO2 insufflation has the same safety and reliability. Furthermore, colonoscopy with CO2 insufflation possesses the significant advantages of less abdominal pain, shorter examination time and better toleration in elderly patients.