The invention relates to steel used for third-generation key nuclear power equipment. The steel comprises the following components by weight: 0.14 to 0.22% of C, 0.15 to 0.35% of Si, 1.10 to 1.65% ofMn, no more than 0.008% of P, no more than 0.005% of S, 0.20 to 0.40% Cr, 0.35 to 0.65% of Ni, 0.20 to 0.40% Mo, 0.01 to 0.04% of V, no more than 0.25% of Cu and no more than 1.5 ppm of H, with the balance being Fe and unavoidable impurities. The manufacturing method for the steel provided by the invention comprises the following steps: carrying out electric furnace smelting, LF and VD secondary refining, vacuum treatment and casting and forging processes for production; heating steel ingots at a temperature of 1200 DEG C to 1250 DEG C, and preserving the steel ingots at the temperature for more than 2 h; subjecting the steel ingots to rolling at a high temperature and with large rolling reduction, wherein an initial rolling temperature is no less than 1150 DEG C, and a finishing rolling temperature is no less than 900 DEG C, and after rolling is completed, carrying out natural cooling; and subjecting a cooled steel plate to quenching and tempering treatment so as to obtain a finishedsteel plate, wherein quenching temperature is 880 to 920 DEG C, the quenching temperature is maintained for 1 to 3 min/mm, tempering temperature is 635 to 665 DEG C, and the tempering temperature is maintained for 2 to 4 min/mm. The steel provided by the invention has high strength and toughness in two states after quenching and tempering treatment and stimulated post-weld heat treatment.