Abstract: To observe the anti-inflammatory effects of ethanol extract from Conyza canadensis (CME) on dextran sodium sulfate (DSS)-induced ulcerative colitis in mice, the mice were divided into normal control group, model group, low dose and high dose CME groups. Except the normal control group, all the other groups were treated with DSS to induce the ulcerative colitis model, and the low-dose and high-dose CME groups were respectively given 50 mg·kg⁻¹ and 200 mg·kg⁻¹ CME by gavage for 7 days continuously. Body weight, colon length, ratio of colon length/weight, disease activity index (DAI) and histological changes of each group of mice were observed. The levels of colonic myeloperoxidase (MPO), glutathione (GSH), superoxide dismutase (SOD) and malondialdehyde (MDA) and the secretion levels of tumor necrosis factor-α(TNF-α), interleukin-1β(IL-1β) and interleukin-6(IL-6), and expression levels of TNF-α, IL-1β, IL-6, inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (cox-2) were also measured. The results showed CME groups significantly inhibited DSS-induced weight loss, colon shortening and intestinal wall thickening compared with the model group (P<0.05), the length of colon recovered to 7.5 cm (low dose CME group) and 8.6 cm (high dose CME group); CME groups significantly improved the mucosal damage, crypt loss and the degree of inflammation. It also resulted in significant increase of GSH and SOD levels(P<0.05), reduced MPO and MDA levels in the colon tissue. In addition, CME could also significantly inhibit the secretion of inflammatory cytokines (TNF-α, IL-1β, IL-6) and the transcription of mRNA of iNOS, COX-2, TNF-α, IL-1β, and IL-6 in colon tissues. Overall, CME had anti-inflammation effects on DSS-induced colitis mice by inhibiting the secretion of inflammatory cytokines and the expression of inflammatory mediators in colon tissues.