YBCO films were grown on (001) YBCO single crystal substrates using the off-axis RF magnetron sputtering method. The interface between the substrate and the film was observed using TEM. The crystal orientation of the film was found to be dependent on the growth temperature. C-axis oriented films with smooth interfaces and holes on their surfaces were obtained at 760 degrees C. A-axis oriented films grown at 580 degrees C surfaces, but the interface rather poor. Lattice mismatches occurred atthe interface due to deoxidization and oxidization of the substrate during the film growth process.