Abstract：Objective：To observe the clinical efficacy of Jianpi Yichang Prescription combined with Mesalazine in the treatment of ulcerative colitis （UC） of spleen deficiency and dampness accumulation type in mild to moderate active stage， and to investigate its effects on inflammatory factors and intestinal microbiota. Methods ： A total of 98 patients with mild to moderate active stage UC of spleen deficiency and dampness accumulation type who were treated at Quzhou Hospital of Traditional Chinese Medicine from January to October 2024 were selected and randomly divided into the observation group and the control group using the random number table method，with 49 cases in each group. The control group received Mesalazine Enteric-Coated Tablets， while the observation group received Jianpi Yichang Prescription in addition to the control group's treatment. Both groups were treated continuously for four weeks. Clinical efficacy， modified Mayo score， Baron score， traditional Chinese medicine syndrome score， levels of inflammatory factors， intestinal microbiota counts， and recurrence rates were compared between the two groups. Results： After treatment，the total effective rate in the observation group was 93.88% （46/49），which was significantly higher than 79.59% （39/49） in the control group （P＜0.05）. After treatment， the modified Mayo scores， Baron scores， and traditional Chinese medicine syndrome scores decreased in both groups compared with those before treatment （P＜ 0.05），and these scores in the observation group were lower than those in the control group （P＜0.05）. After treatment， serum levels of interleukin-6 （IL-6），interleukin-1β （IL-1β），and tumor necrosis factor-α （TNF-α） decreased in both groups compared with those before treatment （P＜0.05），and the levels of these three inflammatory factors in the observation group were lower than those in the control group （P＜0.05）. After treatment，the counts of Escherichia coli and Enterococcus decreased in both groups compared with those before treatment （P＜0.05）， and the counts in the observation group were lower than those in the control group （P＜0.05）；the counts of Bifidobacterium and Lactobacillus increased in both groups compared with those before treatment （P＜0.05），and the counts in the observation group were higher than those in the control group （P＜0.05）. The recurrence rate in the observation group was 4.35% （2/46）， which was lower than 20.51% （8/39） in the control group （P＜0.05）. Conclusion： Jianpi Yichang Prescription combined with Mesalazine is more effective than Mesalazine alone in the treatment of mild to moderate active stage UC of spleen deficiency and dampness accumulation type. The combined therapy can more effectively alleviate symptoms， control intestinal inflammation，regulate intestinal microbiota，and reduce the recurrence rate.