Abstract：Objective：To observe the clinical effect of gargle of modified Gancao Xiexin tang for oral mucositis induced by chemotherapy with 5- fluorouracil. Methods：A total of 120 cases of patients with oral mucositis induced by chemotherapy with 5-fluorouracil were divided into the control group，the western medicine group，and the treatment group according to the random number table method，40 cases in each group. The control group rinsed with normal saline for treatment；the western medicine group was given oral administration of vitamin C and vitamin B2；the treatment group rinsed with modified Gancao Xiexin tang. All groups were continuously treated for one week. The clinical effect was compared among the three groups. The improvement in the degree of oral mucositis，as well as the scores of Numerical Rating Scale(NRS) and Quality of Life(QOL) of cancer patients in the three groups were observed. The scores of Treatment Emergent Symptom Scale(TESS) in the three groups were counted. Results：The total effective rate was 67.5% in the control group，80.0% in the western medicine group，and 92.5% in the treatment group；the total effective rate in the treatment group was higher than those in the western medicine group and the control group(P＜0.05)，and the total effective rate in the western medicine group was higher than that in the control group(P＜0.05). After treatment，the degree of oral mucositis in the three groups was improved when compared with that before treatment，and the proportions of oral mucositis in the treatment group on the 3rd and 7th day of treatment were higher than those in the western medicine group and the control group(P＜0.05). On the 3rd and 7th day of treatment， the score of oral mucositis grading in the three groups were increased when compared with those before treatment(P＜0.05)；the score in the treatment group was higher than those in the western medicine group and the control group(P＜0.05)；the score in the western medicine group was higher than that in the control group(P＜0.05)；the scores of NRS in the three groups were decreased when compared with those before treatment(P＜0.05)；the score in the treatment group was lower than those in the western medicine group and the control group(P＜0.05)； the score in the western medicine group was lower than that in the control group(P＜0.05). On the 7th day of treatment，the QOL scores in the three groups were increased when compared with those before treatment(P＜0.05)；the scores of QOL in the treatment group were higher than those in the western medicine group and the control group(P＜0.05)；the scores of QOL in the western medicine group was higher than that in the control group(P＜0.05). After treatment，the TESS scores in the treatment group were lower than those in the western medicine group and the control group(P＜0.05)；the scores of TESS in the western medicine group were lower than that in the control group(P＜0.05). Conclusion：For patients with oral mucositis induced by chemotherapy with 5- fluorouracil， the gargle of modified Gancao Xiexin tang can effectively relieve pain， improve life quality，and reduce adverse reactions of medicine.