Objective:To observe the clinical efficacy of Dahuang (Rhei Radix et Rhizoma) with acupoint application in preventing and treating constipation caused by Oxycodone Hydrochloride. MethodsSeventy patients of malignant tumors, who were firstly orally treated with Oxycodone Hydrochloride sustained release tablets for relieving pain, were randomly divided into the treatment group and the control group, 35 cases in each group. The control group was treated with no preventive treatment for constipation, and lactulose oral solution was used for symptomatic treatment when constipation during the trial. On the basis of the intervention for the control group, the treatment group was treated with Dahuang by acupoint application at Shenque(CV 8) from the beginning until the end of trial. The treatment course of both groups was 10 days. The incidence of constipation was observed, and the scores of constipation symptoms were compared.  Results:①The incidence rate of constipation was 57.1% in the treatment group and 80.0% in the control group. The incidence rate of constipation in the treatment group was lower than that in the control group.(P＜0.05). ②After treatment,there were statistically significant differences on the score of defecation difficulty and the total score of constipation symptoms(P＜0.05).  Conclusion:Dahuang with acupoint application can reduce the incidence of constipation caused by Oxycodone Hydrochloride, and improve the constipation symptoms of patients.