The GaN hetero-epitaxial layer on sapphire(Al2O3) substrate is studied through scanning electron acoustic microscopy(SEAM) and electron backscattering diffraction(EBSD).The micro-area lattice distortion resulting from the hetero-epitaxy mismatch strain at the interface of GaN and sapphire is observed clearly,and the contrast of the micro-area in concentrated region affected by strain is different significantly.The color code map and quality parameter of the electron backscattering diffraction(EBSD) are used to analyze the variation of the mismatch strain,and the lattice strain and elastic deformation could be released within 200 nm.