Abstract: The amorphous Co(OH)2 obtained from the hydrolysis of CoCl2 under the catalysis of ammoniac base could be deposited on the surface of monodispersed pseudo-spherical α-Fe2O3 nanoparticles to form core-shell particles. After the heat treatment at 500°C, the structure of shell layer crystallized into cubic Co3O4 with a thickness about 6 nm. Different ammoniac bases and their concentrations would affect the structure of the core-shell particles, and it became homogeneous if catalyzed in 1 mol · L^-1 urea solution. TEM and XRD were used to analyze the structure of the core-shell particles. Compared to pure α-Fe2O3 nanoparticles, the UV-Vis spectrum of the core-shell particles showed that their optic properties were changed under photoexcitation and a new absorption peak with maximum absorbance appeared in visible region.