In this article, we report the growth of purely (001) oriented single crystal Y 1 Ba 2 Cu 3 O 7 - x thin films with excellent crystal perfection by afterglow plasma sputtering. Because of little energetic ion and electron bombardment, the crystal perfection of Y 1 Ba 2 Cu 3 O 7 - x thin films was significantly improved. The full width at half-maximum value of the rocking curve around the (005) diffraction peak of the films is 0.12 o . The experiments demonstrate that the afterglow plasma process is very appropriate for the preparation of high-quality Y 1 Ba 2 Cu 3 O 7 - x thin films, which are very sensitive to ion bombardment effects.