本发明属于钢铁材料制备领域，公开了一种疲劳极限大于600MPa的海洋工程用超高强钢及其制备方法。化学成分按重量百分比计为C：0.08～0.11％，Si：0.20～0.50％，Mn：0.70～1.00％，Ni：6.00～8.00％，Cr：0.50～0.70％，Mo：0.80～0.90％，V：0.05～0.08％，P：≤0.003％，S：≤0.001％，其余为Fe和不可避免的杂质。所述超高强钢的钢板制造方法采用控制轧制工艺，随后对钢板进行淬火+回火热处理工艺，钢板的屈服强度≥1000MPa，疲劳极限≥600MPa，‑80℃冲击功≥100J；钢板的微观组织为回火马氏体和VC析出相。

The invention belongs to the field of preparation of steel and iron materials, and discloses ultrahigh-strength steel with the fatigue limit larger than 600 MPa for ocean engineering and a preparation method thereof. The ultrahigh-strength steel comprises the chemical components in percentage by weight: 0.08-0.11% of C, 0.20-0.50% of Si, 0.70-1.00% of Mn, 6.00-8.00% of Ni, 0.50-0.70% of Cr, 0.80-0.90% of Mo, 0.05-0.08% of V, less than or equal to 0.003% of P, less than or equal to 0.001% of S and the balance Fe and inevitable impurities. According to the steel plate manufacturing method of the ultrahigh-strength steel, a controlled rolling process is adopted, then a steel plate is subjected to a quenching and tempering heat treatment process, the yield strength of the steel plate is larger than or equal to 1000 MPa, the fatigue limit is larger than or equal to 600 MPa, and the impact energy at the temperature of -80 DEG C is larger than or equal to 100 J; and the microstructure of the steel plate is tempered martensite and VC precipitated phase.