<p>For the technical challenges in the smelting process of bismuth sulfide concentrate and hazardous characteristics of lead dust, a clean co-smelting process of bismuth sulfide concentrate and lead dust is introduced in this paper. The hazardous waste lead dust (ZnO) is used as a sulfur-fixing agent to recover metallic bismuth and lead from furnace charge by reductive sulfur-fixing smelting. This process fixes elemental sulfur into iron matte, avoiding the emission of sulfur-containing gases. The mechanism of bismuth extraction and sulfur fixation in co-smelting was revealed by thermodynamic calculations and phase transformation experiments. Under the reducing atmosphere, PbSO₄ in lead dust was firstly reduced to PbS, then Bi₂S₃ and PbS interacted with ZnO to form Bi₂O₃, PbO, and ZnS, and finally intermediate products, Bi₂O₃ and PbO, were reduced to metallic bismuth and lead. The feasibility and reliability of this technique were confirmed by process simulation experiments. Under the optimum conditions (W_Bismuthine:W_{Lead dust}:W_Na2CO3:W_Coke = 10:6:15:1, 900&#xa0;°C, 60&#xa0;min), the bismuth recovery rate and sulfur-fixing rate were 98.57% and 97.32%, respectively, and the grade of crude bismuth was 89.81%. This technique provided a new solution for bismuth extraction and lead-bearing solid waste environmentally-friendly disposal. </p>