The micro-segregation of an iron-based multi-component alloy, where the liquid is assumed to be completely mixed and finite diffusion works in the solid, is calculated by a simple method. With this method, not only the solidification path in which the solute distribution ratios change as functions of the composition, but also the solute redistribution profile after solidification can be estimated. As examples, the solidification path and solute redistribution for an iron-carbon-nickel system and an iron-carbon-chromium system have been estimated and compared with the predictions given by assumptions of the equilibrium solidification for carbon and Scheil-type solidification for the metallic solute.