Abstract: The granular materials are composed of a collection of discrete and solid particles, such as coarse sands and debris accumulation. Using data from experiments or based on engineering experiences, numerous models are developed to describe certain mechanical phenomena of granular materials. However, our under-standings of the mechanical properties of granular materials and their physical nature remain limited. The specific mechanical properties of granular materials come from complicated processes of the energy transporta-tion, the disordered structure in the long-range and the ordered structure in the short-range. In this paper, some developments in measuring the inherent structural characteristics, the thermodynamics, and the transformation between solid and fluid states of granular materials are discussed. A new research approach is proposed to unify the thermodynamics and the structural analysis to have a better understanding of granular materials.