The mechanism of chromium accumulation and microstructure transformation of the fused yeast were studied in this paper. The result showed that the process of Cr6+ reduction and adsorption was accompanied by the H+ consumption. The main adsorptive groups on the strain surface included amino, hydroxyl, phosphate group and amide, among which phosphate group played vital role in the chromium accumulation. The removal rate of chromium and reduction rate of hexavalent chromium declined 70% and 46%, respectively, when phosphate group was masked. During the adsorption process the chromium ions complexed on the surface of fused yeast was transported into the cell wall and combined with inclusion to form steady species and this took 90 min to reach the equilibrium. The biosorption and reduction of Cr on the cell surface would alter microstructure of cell surface, reduce cell membrane potential and increase cell membrane permeability.