The invention discloses a high-quality nuclear I-level quenched and tempered steel production method. A quenching and tempering process of negative pressure quenching and high-pressure tempering is adopted. According to the negative pressure quenching process, hearth N2 protection is achieved, the hearth negative pressure ranges from -1.0 MPa to 2.0 MPa, the quenching temperature is AC3+(50-80) DEG C, the total heating time is PLC+(30-50)min, the maximum water amount is larger than or equal to 5200m<3>, and the roller speed is smaller than or equal to 2.0 m/min. According to the high-pressuretempering process, the tempering temperature ranges from 640 to 680 DEG C, the total heating time is larger than or equal to 4.5 min/mm, and discharge air cooling is carried out. According to a steelplate, a grain-refined tempered bainite + little ferrite structure can be obtained in the steel plate through thickness direction, the steel plate uniform and grain refining inner structure is achieved, the grain size reaches 7.5 levels to 8.5 levels, the yield strength is larger than or equal to 650 MPa, the -18 DEG C low-temperature impact toughness average value reaches 120 J or above, the steel plate surface has no oxide skin, and the comprehensive property is excellent.