Objective To discuss the application value of small doses penehyclidine hydrochloride in painless colonoscopy examination. Methods From July 2012 to January 2013, 90 patients who planed to have painless colonoscopy were randomly divided into 3 groups with each group 30 cases. Before anesthesia, giving small doses of penehyclidine hydrochloride to small-dose group, giving conventional dose of penehyclidine hydrochloride to routine-dose group, and giving atropine intravenous administration to atropine group. Observe the smoothly de-gree, and check the heart rate, mean arterial pressure and postoperative adverse reactions of three groups. Results There was no obvious difference among the three groups in trems of smooth degree and oxyhemoglobin saturation. In small-dose group, heart rate and mean arterial pressure before and after the examination were better than that of routine-dose group and atropine group, and there were obviously lower inci-dence of postoperative adverse reaction compared with the routine-dose group and atropine group. Conclusion Giving small-dose of penehy-clidine hydrochloride before anesthesia of painless colonoscopy examination can significantly improve the effect of examination, and it can re-duce the incidence of postoperative adverse reactions.