Abstract: A full relativistic multi-configuration Dirac-Fock theory with quantum electrodynamical (QED) effect and Berit correction was employed to calculate the magnetic quadrupole 3s²¹S₀-3s3p³P₂(Z=20-103) transition energy level intervals, transition wavelengths, transition probabilities and oscillator strengths for Mg-like ions. The results, which consider the finite volume size effect, Breit and QED corrections, were used for comparsing with the recent experimental data. The results show that the magnetic quadrupole transition probabilities of highly ionized atom ions are in accordance with those of neutral atomic allowed transitions and cannot be ignored in the laser plasma of high temperature in ICF and MCF fusions. The effects of the magnetic quadrupole transition of highly ionized atom ions should be considered in the calculation of dielectronic recombination process, opacity, free path and so on.