The invention discloses a method for producing a high-thickness Z-direction steel plate, which comprises the following steps: smelting molten steel in an electric furnace, refining the molten steel in an LF refining furnace, and subjecting the molten steel to vacuum treatment in a vacuum degassing furnace; casting the smelted molten steel; remelting electroslag, heating, rolling into a sheet, cooling and performing hydrogen diffusion treatment; performing the ultrasonic flaw detection of the steel plate subjected to hydrogen diffusion treatment; and normalizing the steel plate subjected to flaw detection to obtain the finished thick steel plate. The method has the advantages that: 1) the strength and toughness of the steel plate are well matched, the yield strength of the steel plate is 334 to 380Mpa, the tensile strength of the steel plate is 508 to 555Mpa, the impact power of the steel plate at 1/2 thickness point and at 20 DEG C below zero is more than or equal to 100J, and the elongation of the steel plate is more than or equal to 23 percent; 2) the lamellar tearing resistance of the steel plate is high, and the Z-direction shrinkage PsiZ of the steep plate at a 1/4 thickness point and a central point is more than or equal to 35 percent; 3) the steel quality of the steel plate is purer, the phosphorus content of the steel plate is less than or equal to 0.008 percent, and the sulfur content of the steel plate is less than or equal to 0.002 percent; 4) the reduction Psiz of the cross section of the steel plate is 39 to 75 percent according to GB5313 standards and is 46 to 79 percent according to EN10164 standards; 5) the internal quality of the steel plate is more compact and meets requirements of JB/T4730-2005I flaw detection standards; and 6) the maximum thickness of the steel plate of the invention is up to 300 millimeters.