A new rare earth iodate K2Y(IO3)5 has been synthesized by hydrothermal method in this paper. Its structure was determined by single crystal diffraction. The results show that K2Y(IO3)5 crystallizes in triclinic crystal system with P1 space group. Its crystal cell parameters are a=10.069(6) , b=8.418(1) , c=11.754(2) , α=109.664(5)°, β=90.518(6)°, γ=91.565(5)°, Z=2. The structure of K2Y(IO3)5 features a zero-dimensional ［Y2(IO3)10］4- anion group, which further linked by K—O polyhedrons to construct the whole framework. In addition, UV-Vis-NIR diffuse reflection spectroscopy shows that K2Y(IO3)5 has a wide transmission range about 0.25~12.46 μm. TG-DSC indicated that the thermal decomposition temperature of K2Y(IO3)5 is 365 ℃. Meanwhile, the band structure of K2Y(IO3)5 is also calculated using first principles. The results shows that the I-5p and O-2p orbits dominate the optical properties of the structure.