Objective To observe the curative effect of Kouchuang Yin on recurrent oral ulcer in clinic. Methods The patients （n=60） with recurrent oral ulcer were divided into the treatment group and control group （each n=30）. The treatment group was given Kouchuang Yin and control group

Kouyanqing Keli. A therapeutic course was 3 months. The total numbers and interval of ulcer were observed for judging long-term curative effect. Results The cure rate

obvious effective rate and total effective rate were all higher in the treatment group than those in the control group. The total numbers of ulcer were less in the treatment group than those in the control group

and the total interval of ulcer was longer in the treatment group than that in the control group. Conclusion Kouchuangyin Keli had a significant advantage in decreasing ulcer numbers and prolonging the interval.