Abstract: The colloids of α-Fe2O3 and ZnFe2O4 have been synthesized with a sol-gel method. Then the heterostructures with different thickness matching for α-Fe2O3 and ZnFe2O4 were fabricated on ITO conductive glass. The results of XRD show that α-Fe2O3 and ZnFe2O4 components can be indexed as the well-crystallized structures for each heterostructure. Moreover, all of composite films present the absorption characteristics of the composite structure, but there is not the obvious difference for these absorption spectra. The signals of steady state surface photovoltage spectroscopy indicate that the heterojunction with the thicknesses of 1.3 μm (α-Fe2O3) and 1.8 μm (ZnFe2O4) presents the highest photovoltage signal. Under the same positive bias,there is the highest photovoltage with the thicknesses of 1.3 μm (α-Fe2O3) and 1.8 μm (ZnFe2O4) under each bias.