Abstract: The present application discloses a high-toughness ultrahigh-strength steel and a manufacturing method thereof, and belongs to the technical field of metal materials. The present application is intended to solve the problem that the existing low-alloy ultrahigh-strength steel has poor toughness and poor hardenability. The high-toughness ultrahigh-strength steel includes the following elements in mass percentages: C: 0.27% to 0.35%; Si: 1.10% to 1.70%; Mn: 0.70% to 1.10%; Cr: 1.00% to 1.40%; Ni: 0.10% to 0.50%; Mo: 0.05% to 0.50%; W: 0.05% to 0.10%; Nb: 0.01% to 0.04%; and iron and unavoidable impurities: the balance. The high-toughness ultrahigh-strength steel of the present application has excellent strength, toughness and hardenability.