Co:BaTiO3 nano_composite thin films on single_crystal magnesia(100) were successfully fabricated by pulsed laser deposition. The morphology and microstructure of the thin films were investigated via atomic force microscope, x_ray diffractometer and Raman spectroscopy. The results show that the thin films consisted o f a highly c_axis oriented tetragonal phase. The surfaces of the thin films were uniform, compact and of atomic smoothness (RMS=015nm). The co particles, of monodisperse distribution, were found to be well dispersed in the matrix Co: BaTiO3. With increasing Co grain size, the intensities of Raman peaks were wea kened and their width broadened.