A nickel-free steel plate used for an ultralow-temperature storage tank used for a boat and a production method thereof are disclosed. The chemical composition of the steel plate includes, by mass, 0.35-0.50% of C, 0.20-0.40% of Si, 22.50-25.50% of Mn, 3.0-4.0% of Cr, 0.020-0.040% of Al, 0.20-0.50% of V, 0.40-0.50% of Cu, 0.020-0.050% of Nb, not more than 0.008% of P, and not more than 0.003% of S, with the balance being Fe and unavoidable impurities. The production method includes smelting, continuous casting, heating and rolling steps. In the chemical component design, the C, the Mn, the Crand the Cu are adopted for solution strengthening, small amounts of the Nb and the V are added to refine crystal grains, and a fully austenitic structure of the steel plate is ensured. The produced steel plate has good comprehensive performance and welding performance, the production cost is low and the application prospect is wide.