Objective To observe the therapeutic effect and possible mechanism of modified Kuijie Fufa Formula（ Formula for ulcerative colitis relaps） for chronce ulcerative colitis（ UC）. Methods Sixty cases of chronic UC were randomized into treatment group and control group

with 30 in each. The patients in the treatment group were orally taken modified Kuijie Fufa Formula one dose daily. The patients in the control group were orally taken 4 g to 6 g sulfasalazine enteric-coated tablets. The treatment lasted for 3 months in both groups. The patients were followed up 6 months after treatment. The endoscopic index score

histological inflammation grade and serum levels of antineutrophil cytoplasmic antibody（ ANCA） were compared before and after treatment in both groups. The comprehensive efficacy and recurrence was determined. Results The comprehensive efficacy and ANCA negative rate was 100% and 90. 91% in the treatment group

which was significantly higher than 74. 07% and 40. 00% in the control group（ P < 0. 05 or P < 0. 01）. The endoscopic index scores were significantly decreased in both groups after treatment and during the follow-up

especially in the treatment group during the follow-up（ P < 0. 05）. The recurrence rate in the treatment group and control group was 17. 86% and 70. 00% respectively

with a significant difference between groups（ P < 0. 01）. Conclusion The efficacy of modified Kuijie Fufa Formula is superior to that of sulfasalazine enteric-coated tablets with a lower relapse

which may be relevant to increasing the negative rate of ANCA.