The present invention relates to a rack steel plate with a thickness up to 177.8 mm by a continuous casting slab, the constituents and mass percentages including C0.11∼0.15%, Si0.15∼0.35%, Mn0.95∼1.25%, P≤0.010%, S≤0.002%, Cr0.45∼0.75%, Mo0.4∼0.6%, Ni1.3∼2.6%, Cu0.2∼0.4%, Al0.06∼0.09%, V0.03∼0.06%, Nb≤0.04%, N≤0.006%, B0.001∼0.002%, the balance is Fe and unavoidable impurity elements. The manufacture method includes, in sequence, KR molten steel pretreatment, converter smelting, LF refining, RH refining, continuous casting through a straight-arc continuous casting machine, shielding the continuous casting slab a cover and slowly cooling, cleaning the continuous casting slab, heating, high-pressure water descaling, control rolling, straightening, slowly cooling, quenching and tempering treatment. The rack steel plate of large thickness in present invention has advantages of high strength, good plasticity and excellent toughness at a low temperature, the process method has advantages of simple process, low cost and efficiently quick etc.