Objective:To observe the clinical efficacy of Quyu Shengxin Formula combined with mesalazine in treating mild to moderate ulcerative colitis(UC). Methods 72 patients with mild to moderate ulcerative colitis were randomly divided into the treatment group and control group,36 cases in each group. The treatment group was treated with Quyu Shengxin Formula and mesalazine,and the control group was only treated with mesalazine,with a course of one month. The clinical efficacy was observed,and the changes of modified Mayo score,life quality scores of UC and the levels of related biochemical indexes including C reactive protein (CRP) and erythrocyte sedimentation rate (ESR) were compared.  Results: ①During the trial,one case in the treatment group fell off due to loss to follow-up,and finally 36 cases in the control group and 35 cases in the treatment group completed the trial.②The clinical total effective rate was 88.57% in the treatment group and 75.00% in the control group. The clinical efficacy of the treatment group was significantly better than that of the control group(P<0.05). ③For the comparison between treatment before and after,there was statistically significant difference on the modified Mayo score in both groups,and the modified Mayo score was significantly decreased in both groups after treatment(P<0.05).For the comparison of the difference of treatment before and after,the difference of the modified Mayo score in the treatment was obviously greater than that in the control group(P<0.05).④For the comparison between the two groups after treatment,there were statistically significant differences on the life quality scores of UC(intestinal symptoms and systemic symptoms),the scores of the treatment group were obviously higher than those of the control group(P<0.05).⑤For the comparison between the two groups after treatment,there were statistically significant differences on the levels of CRP and ESR,the levels of the treatment group were obviously lower than those of the control group(P<0.05).  Conclusion: Quyu Shengxin Formula combined with mesalazine can be used in the treatment of mild to moderate ulcerative colitis,which can significantly relieve the clinical symptoms in active stage,suppress the inflammatory reaction and improve the life quality of patients.