A thin GaN LED film,grown on 2-inch-diameter sapphire substrates,is separated by laser lift-off. Atom force microscopy (AFM) and the double-crystal X-ray diffraction (XRD) have been employed to characterize the performance of GaN before and after the lift-off process. It is demonstrated that the separation and transfer processes do not alter the crystal quality of the GaN films obviously. InGaN/ GaN multi-quantum-wells (MQW's) structure is grown on the separated sapphire sub-strate later and is compared with that grown on the conventional substrate under the same condition by using PL and XRD spectrum.