Abstract: Objective To compare the effect of decreasing sevoflurane inhalation concentration and propofol-remifentanil step-by-step target controlled infusion for the elderly patients with painless colonoscopy. Methods One hundred and sixty patients who may undergo painless colonoscopy were divided into group S(sevoflurane inhalation, n=80)and group P(propofol-remifentanil target controlled infusion, n=80)according to random number table method. Group S was given decreasing anesthesia by mask inhalation of sevoflurane, while the group P was given propofol-remifentanil step-by-step target controlled infusion. Systolic blood pressure(SBP), diastolic blood pressure(DBP), heart rate(HR), pulse oxygen saturation(SpO₂), end-tidal pressure of carbon dioxide(PetCO₂), bispectral index(BIS)were recorded during colonoscopy and at different time points. The time of induction of anesthesia, length of colonoscopic examination time, awaken time, time to leave anesthesia recovery room were recorded. The occurrence of intraoperative hypoxemia, body reaction and adverse reactions were recorded. The incidence of agitation, nausea and vomiting, shivering, abdominal pain during awakening period, and abdominal pain after colonoscopy were recorded. Results Compared with group S, the time of induction of anesthesia was significantly shortened, the incidences of agitation, nausea and vomiting during awakening period, as well as abdominal pain after colonoscopy were significantly - lower(P<0.05). However, no significant differences were found in hemodynamic index at different time points, SpO₂, PetCO₂, BIS before and after the colonoscopy, and in colonoscopy time, awakening time, incidence of shivering and body movement grading(P>0.05). Conclusion Propofol-remifentanil step-by-step target controlled infusion is more suitable for painless colonoscopy in the elderly than the sevoflurane inhalation concentration reduction method.