A new phosphor Sm(IO3)3·2H2O was synthesized under mild hydrothermal conditions. The structure was confirmed by single-crystal X-ray powder diffraction analysis. It crystallizes in the triclinic system with space group P (No.2), a = 7.1570Å, b = 7.4306Å, c = 10.6367Å, α = 95.205°, β = 104.844°, γ = 109.958°. Some characterizations were performed such as Fourier transform infrared spectroscopy (FTIR), powder X-ray diffraction (PXRD), thermogravimetric and differential thermal analysis (TG-DTA), and luminescence spectroscopy. The overall structure of the title compound is two-dimensional. The adjacent iodate layers are further linked with each other by hydrogen bonds to form a three-dimensional supramolecular network. The luminescent properties of Sm(IO3)3·2H2O were studied, the exhibit tunable emission spectra by means of heating treatment.