Objective <p>To observe the effects of acupuncture on intestinal flora and inflammatory factor interleukin (IL)-6 in ulcerative colitis (UC) model rats and to explore the related mechanism of acupuncture in treating UC.</p> Methods <p>Thirty-two Sprague-Dawley rats were randomly divided into a normal control (NC) group, a model (MO) group, a mesalazine (ME) group, and an acupuncture (AC) group, with 8 rats in each group. Rats, except those in the NC group, were given a 2.5% sodium dextran sulfate solution to establish UC models. After successful modeling, rats in the ME group were treated with mesalazine by gavage twice a day for 7 continuous days; rats in the AC group received acupuncture at bilateral Tianshu (ST25) and Zusanli (ST36) with needles retained for 20 min each time, once a day for 7 consecutive days. After intervention, changes in the intestinal flora diversity, colon tissue damage degree, and inflammatory factor expression in each group of rats were evaluated.</p> Results <p>The body mass increased slowly in the MO group compared to the NC group. After intervention, the body mass increased more significantly, colon injuries recovered, and intestinal flora diversity improved in the ME and AC groups compared to the MO group (<i>P</i>&lt;0.05). The IL-6 expression level was higher in the MO group compared to the NC group (<i>P</i>&lt;0.05). The IL-6 expression level decreased in the AC group compared to the MO group (<i>P</i>&lt;0.05).</p> Conclusion <p>Acupuncture at Tianshu (ST25) and Zusanli (ST36) improves body mass loss and colon injuries, regulates intestinal flora diversity, and reduces the expression of inflammatory factor IL-6 in the colon tissue of UC rats, therefore alleviating the disease severity of UC.</p>