A method for smelting ultra-advanced duplex stainless steel made of CD3MWN, which is designed for the internal control composition during smelting of duplex stainless steel; wherein C≤0.030 wt%, Si≤0.90 wt%, Mn is 1.20-2.50 wt%, P≤0.020 wt%, S≤0.015 wt%, Cr 26.2-27.5 wt%, Ni 6.2-7.6 wt%, Mo 2.2-3.4 wt%, Cu≤0.80 wt%, W≤0.80 wt%, N 0.32-0.38 wt%, B is 0.0010-0.0100 wt%, Ba is 0.0002-0.0100 wt%, Ce+La is 0.005-0.030 wt%; %Cr+3.3(%Mo+0.5%W)+16%N≥45, precise control of trace The content of elements B, Ba, Ce, and La; increase the N content to more than 0.30%, and at the same time avoid nitrogen pores in the casting; minimize the content of harmful elements such as sulfur, oxygen, hydrogen and other elements, and improve the liquid steel. purity. The poured casting has high strength and excellent corrosion resistance. The ratio of ferrite phase and austenite phase in stainless steel is close to 50%. The service life of the casting is prolonged, the manufacturing cost is greatly reduced, and the goals of energy saving, consumption reduction, and environmental protection are realized.