The invention provides a magnesium chromium fireproof product die carbon and a boron combined penetration treatment process suitable for mass industrial production. In the process, the die is subjected to carburizing treatment and then the boriding treatment; before packaging, impurities and oxides remained on the surface of the die are milled and polished, and cleaned by alcohol and dried; and the die is placed in a boriding box, and the boriding box is placed in a box furnace for boriding treatment. The process has the advantages that for the abnormal 20Cr magnesium chromium fireproof product die with large overall dimension of more than 500 to 1,000mm and complex shape, after the combined treatment of carbon penetration and boron penetration, the depth of penetration is between 0.08 and 0.12mm, the hardness is between 1,300 and 1,500HV, and the wearing resistance and the endurance are both sunstantially improved.