In the present paper, the authors measured the Raman spectra of YAG/Nd : YAG single crystal, Nd : YAG precursor and the powder sintered at different temperatures. The bands of these Raman spectra were assigned and analyzed. The results show that there is a structure transformation process in the course of sintering Nd : YAG precursor. The powder sintered at 700 degrees C was amorphous and it is of AlO4 tetrahedron structure. With the increase in sintering temperatures, the Raman spectra varied mainly in two respects. One is the decrease in FWHM with the increase in the bands intensity; the other is the bands shift. These should be due to the increase in the order degree of the interface component. Additionally, the difference in the lattice vibration modes between the powders sintered at 800 degrees C and the Nd : YAG single crystal powder was caused by the contribution of the interface component.