Electrodeposited Zn-Fe alloy coating has good anti-corrosion performance and has been widely applied to protect steel materials from corrosion. In this paper, Zn-Fe alloy coatings were plated from acidic sulphate bath, and the relationship between real concentration of metallic complexes ([ZnL+] and [FeL+]) in the bath, which was calculated through solving nonlinear equations by METLAB software, and components of alloy coatings was studied. When ZnSO4•7H2O added in the bath increases from 10 g/L to 50 g/L, the ratio of ferrous complex to total complex decreases from 81.96% to 46.76%, simultaneously the iron content in Zn-Fe alloy coatings decreases from 26.82% to 6.32%. As FeSO4•7H2O and (NH4)2SO4 added in the bath increases from 40 g/L to 80 g/L respectively, the ratio of ferrous complex to total complex increases from 50.02% to 66.23% and from 58.65% to 60.37% respectively, simultaneously the iron content in coatings increases from 8.26% to 13.77% and from 9.28% to 11.92% respectively. The results show that variation of concentration of metallic complexes in the bath can lead to variation of components of coating proportionally.