Objective To investigate the effect of connexin 43 (Cx43) on M1 polarization of mouse RAW264.7 macrophages induced by lipopolysaccharide (LPS). Methods RAW264.7 macrophages were cultured in vitro and randomly divided into four groups: control group, LPS group, LPS combined with Gap19 group, LPS combined with Gap26 group. The protein levels of Cx43 and M1 polarization marker CD86 and inducible nitric oxide synthase (iNOS) in mouse RAW264.7 macrophages were detected by Western blot analysis. The expression and localization of CD86 in RAW264.7 macrophages were observed by immunofluorescence cytochemistry, and the expression frequency of M1 polarization marker CD86 in mouse RAW264.7 macrophages was detected by flow cytometry. Results Compared with the control group, the protein expression of CD86, iNOS and Cx43, as well as the expression frequency of CD86 in LPS group showed a significant increase. However, compared with LPS group, the protein expression of CD86 and iNOS, and the expression frequency of CD86 decreased significantly in LPS combined with Gap19 group and LPS combined with Gap26 group. As such, LPS could induce M1 polarization of macrophage, while Gap19 and Gap26 can reduce the expression of M1 polarization markers. Conclusion M1 polarization of macrophages can be inhibited by blocking Cx43.