Objective Epithelial-to-mesenchymal transition (EMT) has been proven to be involved in the development and progression of fibrosis diseases. This study aims to investigate the related mechanism of Interleukin-33-induced EMT through M2 macrophages. Methods Twenty-five male BALB/c mice were divided into oral mucosal fibrosis (OSF) group with 20 mice and control group with 5 mice. In OSF group, the mouse model of OSF was established by arecoline stimulation, and the expression levels of macrophage phenotype, IL-33 and transforming growth factor-β 1 (TGF-β 1)/Smad (small mothers against Decappentaplegic) in oral mucosa were observed. The human oral mucosa cells were cultured and interacted with M2 macrophages in vitro. IL-33 additive and TGF-β receptor inhibitor were used to observe the expression level of EMT markers.Results The model of OSF mice was successfully established and confirmed by HE stain and Masson's trichrome stain. At the same time, we found evidence in support of EMT, such as decreased protein levels of E-cadherin and elevated levels of Vimentin in the oral mucosa(P＜0.05). Additionally, the increasing of IL-33 and TGF-β levels as well as TGF-β1/Smad signaling activation was observed(P＜0.05). Macrophages were recruited to the oral mucosa and identified as M2 macrophages. Compared with the blank control group, level of E-cadherin in IL-33 group decreased and the expression of Vimentin increased (all P＜0.05). Compared with IL-33 group, the expression of E-cadherin in LY-2109761+IL-33 group increased and the level of Vimentin decreased (all P＜0.05). The expression levels of TGF-β, p-Smad2 and Smad2 were detected by Western blot. Compared with IL-33 group, IL-33 in LY2109761+IL-33 group promoted TGF-β (P＜0.05). Compared with the blank control group, the level of p-Smad2 in IL-33 group was significantly increased (P＜0.05). Compared with IL-33 group, the level of p-Smad2 in LY-2109761+IL-33 group decreased significantly (P＜0.05).Conclusion IL-33 conducts M2 macrophages activating TGF-β1/Smad signaling pathway to promote EMT of the oral mucosa