The invention provides a method for duplex smelting for high-nitrogen steel through pressurized ladle refining and pressurized electroslag remelting, and belongs to the technical field of high-nitrogen steel smelting. According to the invention, nitrogen alloying, deep deoxidation and deep desulfurization are sequentially carried out on molten steel in a pressurized steel ladle, and meanwhile, efficient nitrogen alloying is realized in the nitrogen alloying process in the mode that nitrogen bottom-blowing and pressurized gas phase-molten steel interface nitriding are combined, so that nitrogen is uniformly distributed, and the content of impurities in the molten steel is reduced through nickel-magnesium alloy and rare earth; and then the pressurized electroslag remelting is carried out, so that the content of inclusions and impurity elements in the molten steel is further reduced, segregation of the steel is improved, and the high-nitrogen steel is uniform and compact in structure. The result of the embodiment shows that the high-nitrogen steel is low in impurity content, uniform and stable in component and capable of meeting the use requirements in the fields of aviation, aerospace, petroleum, chemical engineering, energy, ocean, bioengineering and the like.