The mechanical properties and the point defect energy of magnesium hydroxide（Mg（OH）2） were studied using the molecular dynamics. Moreover, the microelectronic structure of Mg（OH）2 with point defects in the bulk and on its surface were investigated using the first principles. The simulation results indicate that Mg（OH）2 was easily modified by other cations because of its strong, favorable interstitial and substitution defects via point defect energy calculation. Mg（OH）2 can provide high-efficiency flame retardancy because of the strong OH（OH Schottky defect） or H bond（H Frenkel defect and Schottky defect）. The potential model of Mg（OH）2 was established, and molecular dynamics simulation was used to investigate the relations between the crystal structure and the mechanical properties. Mg（OH）2 with special morphology such as nano-sheets was a prior consideration to maintain the composite mechanical properties. The detailed electronic structures of Mg（OH）2 with defects were determined. This work may provide theoretical guidance for choosing dopant element and reveal the element doping mechanism of Mg（OH）2.
