Nonpolar a-plane （1120） GaN has been grown on r-plane （1102） sapphire by metal-orgamic chemical vapor deposition. The crystal quality has been greatly improved by using the AlGaN multiple-quantum-well interlayers. The surface morphology and the crystal quality were investigated by high resolution X-ray diffraction and atomic force microscopy.The triangular pits were eliminated completely. The precession of the X-ray diffraction symmetric reflection peak full with width at half maximum of （1120） is 680″.