The invention relates to a high-toughness and high-strength thick steel plate and a production method thereof. The steel plate comprises the following chemical components in percentage by weight: 0.20-0.24% of C, 0.25-0.36% of Si, 0.50-0.75% of Mn, 1.00-1.20% of Cr, 1.65-2.4% of Ni, 0.28-0.42% of Mo, 0.006-0.018% of Nb, 0.005-0.015% of Ti, and the balance Fe and inevitable impurities. According to the steel plate and the production method thereof, which are disclosed by the invention, an ingredient B-free system is adopted, a reasonable design is carried out on the alloy elements of Mn, Ni, Cr and Mo, the conditions that Mn+Cr is less than Ni, and Si+Mn+Cr+Ni+Mo is greater than 3.8% and less than 5% are met; and through a process of combining quenching, intercritical quenching and tempering, the produced steel plate has a thickness of not less than 80mm, a yield strength Rp0.2 of not less than 1200MPa, a tensile strength Rm of not less than 1450MPa, a percentage elongation of not less than 12% after fracture, a yield ratio of not greater than 0.85, and an impact energy of not less than 65J at minus 40 DEG C, the structure and properties in the whole thickness direction are uniform, the hardness fluctuation is low, and the fluctuation amplitude of the Brinell hardness value of the section is less than 10HB. The steel plate can be widely used in the high-strength and high-toughness super-thick steel plate application fields of various heavy engineering machinery, mining machinery, coal mine machinery, large buildings, bridges, hydroelectric power, ocean platforms and the like.