Abstract： Objective： To observe the effect of umbilical application with Xiaozhang Tongbian powder combined with polyethylene glycol electrolyte powder(PEG) on bowel preparation before colonoscopy. Methods： A total of 100 cases of patients undergoing colonoscopy were randomly divided into the observation group and the control group，50 cases in each group. Before colonoscopy， the control group was given the oral administration of PEG and the observation group was additionally given umbilical application with Xiaozhang Tongbian powder based on the treatment of the control group. The intestinal residual liquid dung volume，the intestinal foam volume，the first defecation time，the time of discharging waterlike stool and the total defecation times in the two groups were compared. The incidences of adverse reactions such as nausea and vomiting， abdominal distension and abdominal pain were recorded. Results： After intervention， the intestinal residual liquid dung volume and the intestinal foam volume of grade Ⅰaccounted for 86.0% respectively in the observation group，obviously superior to those of 52.0% and 60.0% respectively in the control group(P＜0.05). The first defecation time and the time of discharging water-like stool in the observation group were shorter than those in the control group(P＜0.05). There was no significant difference being found in the comparison of the total defecation times between the two groups(P＞ 0.05). The incidence of nausea and vomiting was 26.0% in the observation group， lower than that of 62.0% in the control group(P＜0.05). The incidence of abdominal pain and abdominal distension was 88.0% in the observation group and 80.0% in the control group；the comparison between the two groups showed no significant difference(P＞0.05). Conclusion：During the bowel preparation before colonoscopy， the therapy of umbilical application with Xiaozhang Tongbian powder combined with PEG can decrease the volumes of intestinal residual liquid dung and intestinal foam， shorten the time of bowel preparation，and reduce the incidence of nausea and vomiting.