OBJECTIVE： To observe the clinical efficacy and safety of Vitamin C tablets after grinding for local use in the treatment of oral ulcer. METHODS： Two hundved and eighty-six cases of oral ulcer in our hospital during Feb. 2014-Fed. 2016 were selected and divided into treatment group and control group according to random number tabel， with 143 cases in each group. Control group was given Guilin watermellon frost， 2-3 tirnes a day； treatment group was given Vitamin C tablets powder for local use， 2-3 tirnes a day. Clinical efficacy， the time of ulcer disappearance， the incidence of ADR， recurrence rate of ulcer， treatment satisfactory degree were observed in 2 groups. RESULTS： Total response rate of treatment group was 96.5％， which was significantly higher than 80.4％ of control group， with statistical significance （P＜0.05）. The time of ulcer disappearance was （2.37±0.89） d in treatment group， which was significantly shorter than （4.12±1.33） d of control group； recurrence rate of ulcer was 3.5％， which was significantly lower than 8.4％ of control group； treatment satisfactory degree was 90.9％， which was significantly higher than 79.7％ of control group， with statistical significance （P＜0.05）. There was no statistical significance in the incidence of ADR between 2 groups （P＞0.05）. CONCLUSIONS： Vitamin C tablets after grinding for local use has obvious effect on oral ulcer， significantly shortens the time of ulcer disappearance， reduces recurrence rate， and improves treatment satisfactory degree with good safety.