Objective To investigate the application effect of Rhubarb in colonoscopy of patients with constipation.Methods From January 2019 to June 2021,60 patients with constipation in the Department of Outpatient,the Fourth Affiliated Hospital of Nanchang University were selected as the research objects,and they were divided into group A(20 cases),group B (20 cases) and group C (20 cases) by random number table method.Patients in group A were given raw Rhubarb water 3 d before colonoscopy,and Compound Polyethylene Glycol Electrolyte Powder (PCEP) was taken orally at 8:00 PM 1 day before the examination,and PCEP was taken orally 5 h before the examination.In group B,PCEP was taken orally at 8:00 PM 1 day before the examination,PCEP was taken orally 5 hours in advance on the day of examination,and raw Rhubarb water was taken to enema 1 hour earlier.In group C,PCEP was taken orally at 8:00 PM 1 day before the examination,and PCEP was taken 5 h in advance on the day of examination.Boston bowel preparation scale (BBPS) scores and satisfaction scores were observed and compared among the three groups.The colonoscopy time of the three groups was compared.Results The BBPS score of group A was higher than that of group B and group C,the difference was statistically significant (P＜0.05).The satisfaction score of group A was higher than that of group B and group C,and the difference was statistically significant (P＜0.05).The colonoscopy time of patients in group A was shorter than that in group B and group C,and the difference was statistically significant (P＜0.05).Conclusion In intestinal preparation for patients with constipation before colonoscopy,PGEP combined with Rhubarb oral administration or enema can better achieve the purpose of intestinal moistening and defecation than PGEP alone,and ultimately improve the intestinal cleanliness of patients effectively.