The invention relates to an ultrahigh-strength steel plate of which the yield strength is greater than 1400 MPa. The steel plate is prepared from the following chemical components: 0.22 to 0.30% of C, 0.10 to 0.50% of Si, 0.8 to 1.40% of Mn, 0.010 to 0.040% of Nb, 0.020 to 0.050% of V, less than or equal to 0.008% of Ti, 0.05 to 0.09% of Al, 0.8 to 2.0% of Ni, 0.30 to 0.70% of Cr, 0.30 to 0.70% of Mo, 0.001 to 0.005% of B, 0.001 to 0.005% of Ca, less than or equal to 0.010% of P, less than or equal to 0.003% of S, less than or equal to 0.002% of O, less than or equal to 0.004% of N, less than or equal to 0.00015% of H and the balance of Fe and inevitable impurity elements. The production method comprises the following steps of steelmaking in a converter or an electric furnace, LF refining, VD or RH vacuum degassing, Ca treatment, continuous casting, slow cooling, heating, rolling, quenching and low-temperature tempering. The steel plate has good low-temperature toughness, and additionally, the yield strength is greater than 1400 MPa.