The influence of different concentrations of Mg 2+ ions doping on the structure, morphology and phase transition of LiIO 3 crystal was investigated. The best Mg 2+-doped alpha-lithium iodate ( Mg :α- LiIO 3) crystals for potential optical applications can be successfully grown by the aqueous solution method when the concentration of Mg 2+ ions in the initial mother solutions Cm< 0.001 M. Chemical component analysis shows the Mg :α- LiIO 3 crystal is a new system with the segregation coefficient k>1. The polarized Raman results are consistent with our conclusions that the Mg 2+ ion substitutes for the host Li + cation in the pure α- LiIO 3 crystals and results in the corresponding cation vacancies. As Cm increases, inclusions, spontaneously crystalline grains, β phase of LiIO 3 and hillock-shape Mg :α- LiIO 3 crystals are induced respectively by different concentrations of Mg 2+ ions doping under the same crystal growth conditions. When Cm>0.1 M, the polarized Raman results indicate that larger amounts of Mg 2+ ions incorporated inhibit LiIO 3 growth and result in the hillock-shape morphology by destabilizing the crystal lattice and inducing lattice distortion.