To explore the protective effects and its mechanism of cinnamaldehyde (CA) on ulcerative colitis (UC) mice. Sulfasalazine (300 mg/kg) was used as the positive control,and CA was administered to the UC mice which was induced by 3% dextran sodium sulfate (DSS) at 150, 250, 500 mg/kg doses. Observe the changes in the state of the mice before and after the administration and perform the DAI score,and the morphological changes of mice colon were observed by HE staining and pathological evaluation was performed;ELISA kit and Western blot technology were used to detect the changes of inflammatory factors in the serum of mice and the expression of inflammation-related proteins in the colonic epithelium of mice.The results showed that CA could protect the colonic tissue morphological integrity and improve colonic mucosal injury in UC mice within the experimental dose range;Increase the levels of IL-4, IL-10,reduce the levels of IL-6, IL-8 and TNF-α in serum;up-regulate the expression of NF-κB in the cytoplasm,and inhibit the level of phosphorylated STAT3.In summary,CA has a protective effect on UC mice,which could reduce the degree of colon injury and inhibit inflammation.The more in-depth mechanism need to be further study.