Qing-Chang-Hua-Shi (QCHS) is a Chinese herbal formula, which is composed of 11 herbs. Studies have also shown that QCHS granules can alleviate colitis in animal models by preventing inflammatory responses and suppressing apoptosis through the MEK/ERK signaling pathway. To determine the efficacy and safety of QCHS granules in patients with moderately active UC. We performed a multicenter, randomized, placebo-controlled, double-blind study of patients with moderately active UC who did not respond to 4 weeks of mesalazine therapy at the maximum dose. Patients were randomly assigned to groups and administered QCHS granules (125 g/day, n = 59) or an identical placebo, which was similar to the QCHS granules in color and taste (125 g/day, n = 60), with continued 5-ASA 4 g/d therapy for 12 weeks. The primary outcome was the rate of clinical response and clinical remission at week 12. The secondary outcomes were health-related quality of life, endoscopic response rate, and mucosal healing rate. Any changes in mucus/bloody stool and diarrhea were recorded. Out of the 119 enrolled patients at 10 different centers in China, 102 patients completed the trial. Clinical remission and clinical response were seen in 31.48% and 92.59% of QCHS-treated patients, and 12.50% and 72.92% of placebo-treated patients, respectively. There was a significant difference between the two treatment groups. More patients receiving QCHS granules vs. placebo achieved remission of mucus/bloody stool (70.37% vs. 47.92%, P = 0.0361). Adverse event rates were similar (QCHS granules 38.33%; placebo 25.42%). In conclusion, QCHS granules were superior to the placebo in introducing clinical remission and mucosal healing, as well as in relieving mucus/blood stool in patients with moderately active and 5-ASA-refractory UC. © 2021 The Authors