Objective To explore the mechanism of NLRP3 gene knockout on abnormal mucosal barrier and inflammatory factors in ulcerative col itis (UC) mice. Methods 32 NLRP3 knockout (NLRP3-/-) mice and 30 C57BL/6 wild type (wild-type,WT) mice were randomly divided into 6groups：NLRP3-/-blank group, NLRP3-/-model group,NLRP3-/- mesalazine group,WT blank group, WT model group and WT mesalazine group. Except for the two blank groups, the other groups were given 3% dextran sodium sulfate (DSS) to drink freely for 5 days to establish UC mouse model. Following the successful establishment of the model, each group underwent intragastric administration of the respective solution for a duration of seven consecutive days.The general condition, body weight, DAI score and colon length of mice in each group were observed and evaluated. The histopathological changes of colon were observed by HE staining. The positive expressions of ZO-1, claudin-1, occludin, TNF-α and IL-6 in colon tissue were detected by immunohistochemistry. Results (1) Contrasted with two model groups, the DAI score of NLRP3-/- model group was significantly higher than that of WT model group on the 12th day, and the colon length of WT model group was significantly shorter than that of WT model group（P < 0.01）,the pathological injury of intestinal mucosa was more serious. The expression levels of ZO-1, claudin-1, and occludin in colonic tissue were conspicuously diminished Contrasted to the WT model group, whereas the positive expression of TNF-α and IL-6 were significantly elevated, exceeding those observed in the WT model group; (2) Contrasted with two mesalazine groups, the DAI score of NLRP3-/- mesalazine group was significantly higher than that of WT mesalazine group on the 12th day, and the positive expression of ZO-1, claudin-1 and occludin in colon tissue of NLRP3-/- mesalazine group was lower than that of WT mesalazine group. Conclusion Specific knockout of NLRP3 gene makes mice more sensitive to ulcerative colitis. Contrasted with WT mice, NLRP3-/- UC mice have more severe mucosal barrier injury and release more inflammatory factors. Mesalazine could repair the mucosal barrier of NLRP3-/- and WT UC mice and reduce inflammation, but the mucosal barrier of NLRP3-/-UC mice was more damaged than that of WT mice. Under the same experimental conditions, the repair degree of mesalazine on mucosal barrier of NLRP3-/-UC mice was lower than that of WT mice.