Abstract: Since ultraviolet (UV) light, as well as blue light, which is part of visible light, is harmful to skin, samarium–cerium compounds containing Sm₂O₂S were synthesized by co-precipitation method. This kind of compounds blocks not only UV light, but also blue light. The minimum values of average transmittance (360–450 nm) and band gap of samarium–cerium compounds were 8.90% and 2.76 eV, respectively, which were less than 13.96% and 3.01 eV of CeO₂. Elemental analysis (EA), X-ray diffraction (XRD), Fourier transformation infrared (FTIR), and Raman spectra determined that the samples contained Ce₄O₇, Sm₂O₂S, Sm₂O₃, and Sm₂O₂SO₄. The microstructure of samples was analyzed by scanning and transmission electron microscopies (SEM and TEM). X-ray photoelectron spectrum (XPS) showed that cerium had Ce³⁺ and Ce⁴⁺ valence states, and oxygen was divided into lattice oxygen and oxygen vacancy, which was the direct cause of the decrease of average transmittance and band gap.