The　elastic　strain　field　in　a　GaN/sapphire　structure　was　measured　via　electron　backscatter　diffraction　(EBSD).　Image　quality　and　small　misorientation　of　EBSD　Kikuchi　patterns　as　strain　sensitive　parameters　were　applied　to　evaluate　the　distortion　and　the　rotation　of　crystal　lattices　in　GaN-buffer-sapphire　structure,　as　well　as　to　display　micro-sized　elastic　strain　field.　The　influence　region　of　the　elastic　strain　in　GaN/sapphire　structure　is　about　200700　nm.　The　diffraction　intensities　of　Kikuchi　patterns　were　extracted　and　the　strained/unstrained　regions　in　GaN　epitaxial　structure　were　recognized　by　using　the　fast　Fourier　transform　(FFT).