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• Vertical zone refining method was applied to produce 7 N-grade indium. • Physical fields during multipass vertical zone refining were simulated by finite volume method. • Voller-Beckerman model was introduced to deal with both back-diffusion and coarsening effect on solute microsegregation. • Dynamical interaction between melt flow and solute redistribution was discussed. • A high-efficiency refining routine for indium was suggested and experimentally proved. Horizontal zone refining has been widely used for the production of ultra-pure metals through solidification-induced microsegregation effect. Current research on vertical zone refining is limited, owing to the high-temperature cracking risk of crucible; however, it is highly potential for low-melting metals as demonstrated in this research. The present work comprehensively dealt with both back-diffusion and coarsening effect on the solute redistribution by adopting the Voller-Beckerman (V-B) model. Physical fields, including temperature, melt flow and solute distribution, were numerically simulated based on In–1 wt.%Sn binary alloy by means of finite volume method, and the dynamic interaction between melt-flow and solute distribution was clarified. A high-efficiency processing routine was suggested, and it was experimentally proved that the vertical zone refining was a promising method for producing ultra-pure 7 N-grade indium. [ABSTRACT FROM AUTHOR]