The first rare-earth borate crystal CsBa2ScB8O16 with both zero-dimensional ［B3O6］ units and one-dimensional B—O chain structures has been synthesized by the high-temperature solution method. It crystallizes in the triclinic crystal system with the P1 space group, with lattice parameters of a=6.698 5 , b=7.216 , c=14.798 , α=97.563°, β=95.226°, γ=95.546°, Z=2. In this compound, ［BO3］ and ［B4O9］ units are connected by sharing oxygen atoms to form a one-dimensional chain ［B5O10］∞. Octahedrally coordinated ［Sc(1)O6］ groups and the one-dimensional chain ［B5O10］∞ are further connected by sharing oxygen atoms to form two-dimensional layer ［Sc(1)(B4O9)］∞. Interlayers are linked by octahedrally coordinated ［Sc(2)O6］ groups, which share oxygen atoms to form a three-dimensional Sc—B—O framework. Isolated ［B3O6］ units are filled in the three-dimensional channels with Cs+ and Ba2+ to balance the charges. In order to further explore the novelty of the structure of CsBa2ScB8O16, we compared it with other rare-earth borates containing alkali or alkaline-earth metals, and discuss the effect of the cation-to-boron molar ratio (n(A)/n(B)) on the degree of polymerization of B—O units, as well as the dimensionality of the B—O anion framework. Furthermore, the first-principles calculations, infrared spectrum, UV-vis-NIR diffuse reflectance spectrum and the thermal analysis of the compounds have also been performed. Property measurements show that CsBa2ScB8O16 exhibits short UV absorption edge (＜190 nm) and moderate birefringence (0.072@1 064 nm). The optical properties of the compound are mainly contributed by the ［B3O6］, ［B5O10］ units, and ［ScO6］ octahedra.