Structural analysis is the essential procedure for a better understanding of the underlying nature of nitride phosphors. It is also important to explore the ways to optimize and further improve the luminescence performance of nitride phosphors. Similar to oxide-based phosphors (Blasse and Grabmaier 1994; Yen et al. 2006), the luminescence properties of nitride phosphors are strongly dependent on the composition and crystal structure, in particular the local structure of the dopant sites, i.e., the environment around the activator ions, like Eu2+ and Ce3+, because their 5d electrons are very sensitive to the type of ”rst-and second-nearest coordination atoms, point symmetry, and bond lengths. Numerous techniques have been used for structural analysis. In this chapter, we will focus on the introduction of the applications of x-ray diffraction (XRD), electron microscopy (e.g., scanning electron microscopy (SEM), transmission electron microscopy (TEM), and scanning transmission electron microscopy (STEM)), and x-ray absorption near-edge structure/near-edge x-ray absorption ”ne-structure (XANES/EXAFS) techniques for the typical nitride phosphors. We will not, however, cover these speci”c techniques in detail. Furthermore, as the emerging powerful tools in a combination of experiments, we will discuss the theoretical approaches of ”rst-principles calculations based on the density functional theory (DFT) approximation and molecular orbitals (MOs) cluster calculations on the selected nitride phosphor systems.