Rare earth borates and rare earth sulfides have been widely concerned by researchers in view of their rich crystal structures and diverse physical properties.Recently,a series of sulfide borates RE3S3BO3 were firstly di scovered with special structures by us.1,2 Eu9MgS2B20O41 was obtained using high temperature solid-state metho d.It crystallizes in the hexagonal space group P63/m.Its structure feature BO4 tetrahedra and BO3 planar trian gles constructed 3D polyanionic network [B20O41]22–,which is consolidated by Mg2+ ions.UV-Vis-NIR diffuse reflectance spectrum measurement indicates that its optical energy gap is 1.51 eV.