Large-thickness wear-resisting steel plate based on NQT process and having good -40 DEG C low-temperature toughness and preparing method

The invention discloses a large-thickness wear-resisting steel plate with good low-temperature toughness and a preparing method. The steel plate comprises, by weight percent, 0.16 to 0.18% of C, 0.20to 0.30% of Si, 1.15 to 1.30% of Mn, not larger than 0.010% of P, not larger than 0.002% of S, 0.010 to 0.020% of Nb, 0 to 0.05% of Cu, 0.40 to 0.60% of Cr, 0.45 to 0.60% of Mo, 0.95 to 1.20% of Ni, 0.025 to 0.040% of V, 0.001 to 0.0025% of B, larger than or equal to 0.060% of Alt, 0.002 to 0.004% of Ca, and the balance Fe and trace impurities. The hardenability index of steel is larger than or equal to 140, the wear-resisting index is larger than or equal to 0.59, the steel plate thicknesses ranges from 80 to 100 mm, the NQT process is adopted, the large-thickness wear-resisting steel plate with good -40 DEG C low-temperature toughness is excellent in mechanical property, the steel plate surface hardness ranges from 330 HBW to 380 HBW, the hardness average value in the thickness directionis not lower than the sur