The Fe2O3 particles with diameters of 3-5 nm were encapsulated between the core and the shell of polymer via emulsion polymerization into the heterostructured microspheres, which were observed through TEM images. The photovoltaic response of the composites, which was studied by the electric-field-induced surface-photovoltage-spectroscopy technique, appeared only if there was an external electric field (EEF) and its decay was much slower than that of Fe2O3 nanoparticles themselves. A reasonable energy band model was supposed to explain this phenomena and indicated that the polymer shell acted as an electric-passivation layer of the semiconductor Fe2O3 particles. The charge-separation process in the structure was also analyzed with this model.