Abstract: Duplex stainless steel 2101 has low production cost, excellent performance, and good resistance to NaCl corrosion. Duplex stainless steel 2101 can be used as marine stainless steel. In recent years, duplex stainless steel 2101 has been considered a valuable material. The “electric furnace + argon oxygen decarburization (AOD) + die casting” process was used to produce duplex stainless steel 2101. During the AOD refining process, the changes of temperature and Cr, C, and Si contents were investigated. Results show that the AOD furnace has a good decarburization effect. The C content (mass fraction) decreases from 2.5% to <0.03%. During the reduction period, Si has a good reduction effect on Cr. During the refining process, the most important step is decarburization. However, after decarbonizing to 0.1%, the required conditions become harsh. The factors affecting the decarburization and chromium retention of duplex stainless steel 2101 were analyzed using thermodynamic calculation formulas. The results show that the carbon–chromium balance is mainly affected by CO partial pressure and temperature. The lower the CO partial pressure, the higher the temperature, which is favorable for decarburization. When the CO partial pressure is constant and w_C < 0.1%, the slope of the carbon–chromium equilibrium curve is increasing rapidly with the w_C value decreasing. It means that the increased temperature range becomes larger making decarbonization more difficult, and the lower CO partial pressure is required for further decarburization. Further decarburization under the conditions of P_CO/P₀ = 0.4 and w_Cr = 21.5% is conducted. To reduce w_C to <0.03%, the temperature in the furnace needs to be increased over 1746.1 ℃.