M1 macrophages are classical activated macrophages, which can secrete a variety of pro-inflammatory factors and chemokines to promote the development of inflammation. Our previous studies have demonstrated that 630 nm light-emitting diode (LED) irradiation inhibits the release of inflammatory factors in macrophages. However, the effect of 630 nm LED on macrophage polarization and its molecular mechanism remains unclear. In this study, we evaluated the effect of 630 nm LED irradiation on the polarization of THP-1 derived M1 macrophages and explored the mechanism of its effect on the polarization of M1 macrophages. Human mononuclear cell line THP-1 was cultured in vitro and induced into macrophages by phorbol myristate acetate (PMA). Lipopolysaccharide (LPS) and interferon-γ (IFN-γ) treated cells were polarized into M1 macrophages, which were irradiated by LED with a wavelength of 630 nm and a power density of 40.02 mW/cm2. CCK-8 colorimetry, MTT assay and lactate dehydrogenase (LDH) activity detection kit were used to detect cell viability. Real-time quantitative PCR was used to detect mRNA expression levels of related factors in M1 macrophages. Western blot and immunofluorescence were used to detect the nuclear translocation of STAT1 in M1 macrophages. The results showed that the cell viability of M1 macrophages did not alter after 630 nm LED irradiation. LED irradiation significantly reduced the mRNA expression levels of the interferon regulatory factor 5 (IRF5) and C-X-C motif chemokine ligand (CXCL) 9, 10 and 11 and block the translocation of transcription factor STAT1. Taken together, 630 nm LED inhibits the polarization of M1 macrophages by blocked STAT1 nuclear translocation. This study may provide new therapeutic ideas for the treatment of diseases related to macrophage polarization.