<p>This study systematically investigated the calcium-enhanced carbothermal reduction mechanism of iron-rich zinc-bearing spinel to achieve efficient zinc–iron separation from steel dust. The samples were characterized by multiple advanced techniques including SEM-EDS, XPS, XRD, Raman, and FT-IR, accompanied with thermodynamic calculations. <i>In situ</i> TG-MS combined with normalized analysis first demonstrated that CaO addition significantly promoted the reduction degree and reaction rate and enhanced CO gas evolution. The formation of calcium ferrite (Ca₂Fe₂O₅) was identified as the thermodynamically favorable initial step, which destroyed the stable spinel lattice and promoted the release and volatilization of zinc. Kinetic analysis demonstrated that the reduction process was governed by crystal nucleation and growth, and both the pre-exponential factor and the apparent activation energy increased in the presence of CaO, leading to an overall increased reaction kinetics especially at high temperatures. Phase evolution analysis experimentally confirmed the gradual decomposition of spinel and the stepwise reduction of iron oxides to metallic iron, further validated by thermodynamic calculations. This work thus provides a clear mechanistic insight for the efficient zinc–iron separation and resource utilization of iron-rich zinc-bearing spinel from steel dust.</p>