High-strength steel and preparation method thereof

The invention relates to high-strength steel and a preparation method thereof. The preparation method of the high-strength steel comprises the steps of smelting, rolling, precision forging and heat treatment. The high-strength steel comprises the following chemical components in percentages by mass: carbon, silicon, manganese, chromium, molybdenum, rare earth lanthanum or cerium, nickel, sulfur, phosphorus and the balance of Fe and inevitable impurities. The high-strength steel has high strength (the yield strength is greater than 1300 MPa) and high impact toughness, especially high low-temperature impact toughness; through component design and a heat treatment method, mechanical parts have high strength and high toughness, especially high low-temperature impact toughness; and different from the high-strength steel obtained through a low-temperature deformation mode, high-strength steel obtained through the heat treatment method has the characteristics that the welding difficulty is generally increased due to