A novel one-step solvothermal method was developed and polystyrene (PS)-cobalt ferrite (CoFe2O4) composite nanomaterial (PS-CoFe2O4) was successfully synthesized by this method using ferric chloride hexahydrate (FeCl3 center dot 6H(2)O), cobalt chloride hexahydrate (CoCl2 center dot 6H(2)O), and the monomer styrene as the precursors. Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), and transmission electron microscopy (TEM) demonstrated the successful preparation of the PS-CoFe2O4 composite material, with the two phases of polystyrene and CoFe2O4 being hybridized at the nanoscale and some strong interaction existing between them. The results of thermogravimetric analysis (TGA) indicated that the inorganic component could improve the thermal stability of the polymer PS. Importantly, the magnetic properties of the as-prepared PS-CoFe2O4 samples were found to be superior to those of pure CoFe2O4, prepared under the same conditions (180 degrees C for 12 h). The improved magnetic properties can mainly be attributed to the hybrid structure, the high degree of crystallinity, and the size of CoFe2O4 in the composite material.