High-magnesium covering agent material capable of being used for tundish and preparing method thereof

High magnesia coating agent and a preparation method may be used tundish, it belongs to the field of inorganic non-metallic material. Mass percentage of coating agent is 40% ~ 60% MgO, 10% ~ 30% CaO, 10% ~ 30% SiO2,3% ~ 8% Al2O3 or Fe2O3,1% ~ 10% of CaF2. By mechanical mixing, compressed to form green body at 1300 ℃ premelting fired, and mechanical disruption to 25 microns and 150 microns, can be used to obtain a high magnesia tundish cover material pre-melting agent. The method of the present invention, high magnesium raw materials, melting fast, reducing the tundish coating agent itself hydration problems, and has insulation of the molten steel, the molten steel purification effect, magnesia materials tundish lining erosion smaller.