Objective To observe the preventive and therapeutic effect of oral ulcer cuased by radiotherapy and chemotherapy with gargle of traditional Chinese drugs. Methods In the perventive groups， it was contrasted to observe the attack rate of oral ulcer between the group treated with gargle of Chinese medicine and the control. In therapeutic groups， it was contrasted to observe the difference of curative effect of therapying the oral ulcers who have received general treament between the groups which treated with Chinese medicine and the control. The difference between the groups treated with χ2 test. Results In the preventive groups， the attack rate of oral ulcer was10% and 70% in the control group， two groups difference is significant（P<0.01）. In the therapeutic groups， Clinical response rate in test group and control group were 92.9% and 28.6% respectively， two groups difference is significant（P<0.01）. Conclusion Gargling with Chinese medicine could obviously pervert and treat oral ulcer caused by radiotherapy and chemotherapy. The method is simple and economic. It is suitable to extend.