<p>To achieve efficient recovery of valuable metals and realize the minimization and valorization of metallurgical solid wastes, the co-reduction process of stainless steel dust and copper slag for preparing Fe–Cr–Ni–Cu alloy is proposed. The metal recovery degree, phase reconstruction, and growth kinetics of metal particles were studied to reveal the co-reduction mechanism. The results indicate that during the co-reduction process, interaction between stainless steel dust and copper slag promotes the isolation of FeO, Fe₂O₃, and Cr₂O₃ from the complicated mineral phases and improves the recovery degrees of Fe, Cr, Ni, and Cu significantly. Co-reduction of stainless steel dust and copper slag accelerates the aggregation and growth of metal particles, with the growth index decreasing from 1.72 to 1.37 and the growth rate constant increasing from 0.44 to 0.60. Under optimum co-reduction parameters, a crude alloy containing 73.98% Fe, 19.55% Cr, 3.78% Ni, and 1.36% Cu was obtained, with the corresponding recovery degrees of Fe, Cr, Ni, and Cu being 96.34, 91.04, 96.81, and 96.46%, respectively. The co-reduction processing method is conducive to waste valorization.</p> Graphical Abstract <p></p>