The invention discloses an Mg-containing steel plate for a TMCP (Thermal Mechanical Control Processing) type E460 ultrahigh-strength ship structure and a production method thereof. The steel plate for the ultrahigh-strength ship structure comprises the following components in percentage by mass: 0.05-0.08 percent of C, 0.1-0.35 percent of Si, 1.6-1.9 percent of Mn, less than 0.001 percent of P, less than 0.003 percent of S, 0.02-0.05 percent of Nb, 0.008-0.013 percent of Ti, 0.01-0.03 percent of Als, 0.008-0.015 percent of Mg, 0.2-0.6 percent of Ni, 0.1-0.3 percent of Mo and the balance of Feand trace impurities. According to the invention, the steel plate for the E460 ultrahigh-strength ship structure is successfully produced by controlling low carbon, low phosphorus, low sulfur and micro Mg treatment under the conditions of 4300 wide heavy plate mill conditions; and the standard requirements of classification societies of every country on the ultrahigh-strength E460 level ship plate steel are met.