Objective To explore the mechanism of NLRP3 gene knockout in relation to the abnormal mucosal barrier and inflammatory factors in ulcerative colitis (UC) mice. Methods Thirty-two NLRP3-knockout (NLRP3^{- / -}) mice and 30 C57BL / 6 wild-type (WT) mice were divided randomly into six groups: NLRP3^{- / -}blank,NLRP3^{- / -} model, NLRP3^{- / -}mesalazine, WT blank, WT model, and WT mesalazine groups. Except for mice in the two blank groups, mice in the other groups were given 3% dextran sodium sulfate to drink freely for 5 days to establish an UC mouse model. After successful establishment of the model, mice in each group underwent intragastric administration of the respective solution for 7 consecutive days. The general condition, body weight, disease activity index (DAI) score, and colon length were observed and evaluated in each group. Histopathological changes in the colon were observed by hematoxylin and eosin staining. ZO-1, claudin-1, occludin, tumor necrosis factor (TNF)-α and interleukin ( IL)-6 expression in colon tissue were detected by immunohistochemistry. Results (1) The DAI score was significantly higher in the NLRP3^{- / -} model group compared with the WT model group on day 12, while colon length was significantly shorter and pathological injury of the intestinal mucosa was more serious. Expression levels of ZO-1, claudin-1, and occludin in colon tissue were lower whereas expression levels of TNF-α and IL-6 were significantly higher in the NLRP3^{- / -} model group compared with the WT model group. ( 2) Regarding the two mesalazine groups, the DAI score was significantly higher and expression levels of ZO-1, claudin-1, and occludin in colon tissue were lower in the NLRP3^{- / -}mesalazine compared with the WT mesalazine group on day 12. Conclusions Specific knockout of the NLRP3 gene makes mice more sensitive to UC. Compared with WT mice, NLRP3^{- / -}UC micehave more severe mucosal barrier injury and release more inflammatory factors. Mesalazine could repair the mucosal barrier and reduce inflammation in NLRP3- / -and WT UC mice. Under the same experimental conditions, mesalazinerepaired the mucosal barrier more effectively in WT compared with NLRP3^{- / -}UC mice.