Abstract: The lateral epitaxy overgrowth （LEO） of GaN was studied experimentally. In order to realize the selective area growth, the surface of the GaN layers grown by conventional MOCVD used as the substrate for LEO must be smooth enough and with perfect crystallographic plane.And the lateral growth rate is dependent strongly on the direction of the mask layer. By using the proper growth process, the GaN samples grown by LEO were successfully obtained. The X-ray diffraction peak width （FWHM） for the LEO samples is 1/3 less than that of the samples grown by conventional MOCVD.