The invention which belongs to the technical field of steel concretely discloses an extra thick quenched and tempered steel plate for an ocean platform tooth bar and a production method thereof. The extra thick quenched and tempered steel plate for the ocean platform tooth bar comprises the following components, by weight, 0.14-0.18% of C, 0.15-0.35% of Si, 0.95-1.30% of Mn, equal to or less than0.015% of P, equal to or less than 0.005% of S, 2.35-2.55% of Ni, 0.35-0.55% of Cr, 0.40-0.60% of Mo, 0.020-0.050% of Nb, 0.010-0.030% of Ti, 0.020-0.045% of total Al, and the balance Fe and inevitable impurities, and the thickness of the steel plate reaches 177.8mm. The extra thick quenched and tempered steel plate for the ocean platform tooth bar, which is prepared through carrying out steps ofsmelting by an electric furnace, steel ingot casting by a die, TMCP rolling, fully enclosed quenching and tempering by a well type heating furnace, and the like, has the advantages of high yield strength, good elongation, excellent Z-directional performance, good low temperature impact toughness, good layered tearing resistance, and low production cost.