The invention discloses a large-thickness SA738GrB steel plate for nuclear island equipment and a production method thereof. The steel plate includes, by weight, 0.05%-0.20% of C, 0.15%-0.55% of Si, 0.90%-1.60% of Mn, 0-0.009% of P, 0-0.006% of S, 0-0.30% of Cr, 0-0.30% of Mo, 0-0.35% of Cu, 0-0.60% of Ni, 0-0.07% of V, 0-0.04% of Nb, 0-0.03% of Ti, and the balance Fe and inevitable impurities. The production method includes the steps of smelting and casting, heating of steel ingots, rolling of the steel ingots and thermal treatment of the steel plate, specifically, the thermal treatment process includes the quenched-tempered thermal treatment process. The compound reinforcement of the steel plate is achieved through micro-alloy elements, and match between strength and toughness is excellent; grains of the steel plate are uniform and tiny, and the normal-temperature stretch property, the high-temperature stretch property and the low temperature impact property of the delivery state and the die welding state all meet the technical requirements; the steel plate contains relatively little additive noble metal, thereby being low in cost and having market competitiveness; the steel plate also meets the demand of a nuclear power project, and accordingly the steel plate can be widely applied to manufacturing of core equipment for nuclear power projects both in China and abroad.