In this chapter, the modeling techniques of the thermodynamic and diffusion properties based on density functional theory in ionic materials, specifically oxide ceramic materials or ionic conductor materials are reviewed. Section 1 is the introduction of this book chapter. Section 2 is devoted to introduce the modeling methods of first-principles finite temperature thermodynamics, including quasi-harmonic phonon calculations and the Debye model. In the phonon model, the frozen phonon method, the linear response method, and the newly developed mixed-space method to model ionic polar materials are discussed. Section 3 introduces the general atomic diffusion theory, first-principles transition state calculations (double-well approach), and ab initio molecular dynamics simulations of the diffusion coefficients in ionic materials. Section 4 discusses some of the recent works of first-principles prediction of the thermodynamic and diffusion properties of ionic materials from our group and in the literature, with a focus on oxides for energy applications. Section 5 summarizes this book chapter.