As the progress of the precision of optical analysis material, Raman spectra is developed as a popular optical and material analysis method. The samples of Raman spectra are low population and prepared easily and fast. Raman spectra would not destroy the samples. GaN is an ideal blue light substrate and a popular nitrogen compound of semi-conductor in III-V group . The character of the GaN is it has a wild direct band gas, high thermal conductivity and high chemical stability. This study is focus on analyzing if there is any difference of the structure of GaN growing on the different substrates. It is compared with photoluminescence spectrum to make sure the accuracy of the result of Raman spectra.