BACKGROUND Banxia Xiexin decoction (BXD), one of a traditional Chinese medicine chronicled in Shang Han Lun, is commonly used to treat gastroenteritis, ulcerative colitis and diarrhea. In our study, we used current biomedical approaches to investigate the therapeutic efficacy of BXD and possible protective mechanism involved in inhibiting dextran sulfate sodium (DSS)-induced chronic ulcerative colitis model. METHODS Chronic DSS colitis was induced in C57BL/6 male mice by three cycles of 5 days of 2% DSS in drinking water, alternating with 5 days of normal water, totaling 30 days. In BXD group, the mice were administered at a dose of 8.7g/kg BXD for 5 days before and during DSS treatment via oral gavage per day. Mice in vehicle group and DSS group were given orally the same volume of drinking water, instead. Body weight, stool characters and hematochezia were observed everyday. The colorectal tissues were used to detect levels of TNF-α, IL-4, IL-10, IL-1β, IL-17, IL-23 and MPO by ELISA or qRT-PCR. The expression of COX-2, 8-Oxoguanine and Nrf2 were examined by IHC, and p-p65 was examined by western blotting. ThOD and the content of MDA were measured according to kits respectively. RESULTS BXD significantly protected against DSS-induced chronic ulcerative colitis by amelioration of body weight loss, DAI and histology score. The level of TNF-α, IL-1β, IL-17, IL-23, COX-2 and p-p65 were decreased significantly, while the level of IL-10 improved with the treatment of BXD. MDA, MPO and 8-Oxoguanine were decreased, meanwhile SOD activity and Nrf2 expression were elevated significantly by BXD. CONCLUSIONS BXD possesses the potential of anti-inflammation and anti-oxidation to treat colitis. The protective mechanism of BXD may involve in inhibition of NF-κBp65 activation and increasement of Nrf2 expression in colorectums of mice.