Magnesium oxide for high-temperature-resistant, high-pressure-resistant, moisture-proof and fireproof cable as well as preparation method and application of magnesium oxide

The invention provides magnesium oxide for a high-temperature-resistant, high-pressure-resistant, moisture-proof and fireproof cable, and a preparation method and application of magnesium oxide. The magnesium oxide for the high-temperature-resistant, high-pressure-resistant, moisture-proof and fireproof cable comprises the following components in percentage by weight: greater than or equal to 96% wt of MgO; less than or equal to 1.0% wt of CaO; less than or equal to 0.45% wt of Fe2O3; less than or equal to 0.3% wt of Al2O3; less than or equal to 2.0% wt of SiO2; AND less than or equal to 0.2% wt of lOI. The invention further discloses a preparation method of the magnesium oxide for the high-temperature-resistant, high-pressure-resistant, moisture-proof and fireproof cable. The magnesium oxide does not need to be baked before cable preparation, and the preparation method is simple and easy to implement; and the breakdown resistance of the cable prepared from the cable can reach up to 3000V at the maximum in an