Objective To observe the clinical effects and safety of Chaihu ⁃Guizhi ⁃Ganjiang decoction for treating recurrent oral ulcer（ROU）. Methods A total of 86 outpatients，meeting the diagnostic criteria of ROU and the Chinese medical syndrome pattern of gallbladder⁃heat with spleen⁃deficiency were assigned to two groups by the random number table. The observation group with 46 participants took Chaihu ⁃Guizhi ⁃Ganjiang decoction orally. The control group of 40 cases gargled Kangfuxin liquid combined with oral administration of vitamin B2 tablets. The two groups both received their treatments for 4 weeks. The sore terminating time and the healing time of oral ulcer wound were recorded after 7 days of treatment ，so were the ratios of qualitative variation of feces as well as the recurrence rates in 12 months after the 4⁃week⁃treatment period. Results The overall response rate of the observation group was significantly higher than that of the control group（84.78% vs. 72.5% ，P < 0.05）. There were no significantly statistical differences between the two groups concerning the average time of sore terminating and the healing time of oral ulcer wound（P > 0.05）. The ratio of improved semiliquid stool in the observation group was statistically significantly higher than the control group（P < 0.05）. The recurrence rates recorded from the follow⁃ups at 1st month，3rd month，6th month and 12th month，were al significantly lower than the control group ，respectively （P < 0.05）. Conclusion Chaihu ⁃Guizhi ⁃Ganjiang Decoction is effective and safe in the treatment of the ROU and it helps to reduce the recurrence rate within 1 year after a treatment period as well.