Abstract： Objective： To observe the clinical effect of Kouyanqing Granules combined with Ranitidine and vitamin C on recurrent oral ulcer (ROU). Methods： A total of 108 cases of patients with ROU were selected and randomly divided into the treatment group and the control group according to the random number table method， with 54 cases in each group. Finally， 52 cases in each group completed the trial (two cases in each group were excluded during treatment). The control group was treated with Ranitidine and vitamin C， and the treatment group was additionally treated with Kouyanqing Granules based on the treatment of the control group. Both groups were treated for seven days. The clinical effects，the traditional Chinese medicine (TCM) syndrome scores，the levels of oxidative stress indexes [serum malondialdehyde (MDA)，superoxide dismutase (SOD)] and serum inflammatory factors [tumor necrosis factor-α (TNF-α)， hypersensitive C-reactive protein (hs-CRP) and interleukin-6 (IL-6)] and the recurrence rates were compared between the two groups. Results： After treatment， the total effective rate was 100% in the treatment group and 88.46% in the control group， the difference being significant (P＜0.05). After treatment， TCM syndrome scores in the two groups were decreased when compared with those before treatment (P＜0.05)， and the TCM syndrome score in the treatment group was lower than that in the control group (P＜0.05). After treatment，the serum MDA levels in the two groups were decreased when compared with those before treatment (P＜0.05)， and the serum SOD levels were increased when compared with those before treatment. The serum MDA level in the treatment group was lower than that in the control group (P＜0.05)，and the serum SOD level in the observation group was higher than that in the control group (P＜0.05). After treatment， the levels of TNF- α， hs-CRP， and IL-6 in serum in the two groups were decreased when compared with those before treatment (P＜0.05)， and the above three indexes in the treatment group were lower than those in the control group (P＜0.05). After three months of follow-up，the recurrence rate was 7.69% in the treatment group and 21.74% in the control group，the difference being significant (P＜0.05). Conclusion： Kouyanqing Granules combined with Ranitidine and vitamin C has a significant curative effect in the treatment of patients with ROU，which can relieve the TCM syndromes of patients， regulate the antioxidant capacity of the body， reduce inflammatory responses， and reduce the recurrence rates.