The structural and thermoelasticity of antifluorite magnesium silicide at high temperatures were studied by using the plane-wave pseudo-potential method in the framework of density functional theory.The bulk ground-state quantities such as lattice constants,cell volumes,band structures and elastic constants were calculated. It showed that the elastic constants of Mg2Si were well consistent with the experimental data under ambient conditions. The crystal cell volume and bulk modulus of Mg2Si as functions of applied temperature were also presented.The lattice dynamics was applied to determine the phonon dispersion curves.To complete the fundamental characterisation of this crystal,the coefficients of thermal expansion (CTE),isochoric heat capacities and Debye temperature of Mg2Si in the whole temperature range from 0 K to 1300 K and pressure range from 0 GPa to 7.48 GPa were investigated.The results were in favourable agreement with the previous theoretical calculations and the existing experimental data.