Abstract: The geological disasters caused by avalanche, large scale deformation, and flow slide of the geo-granular materials have brought massive destruction and potential threats to national economic development and security of lives and property of the people. Most of the geological materials causing those geological disasters can be classified as granular materials. The integration of geological disaster and granular material mechanics is always one of the most important directions for researchers in both soft matter and geological engineering. Granular materials are composited by many individual granules, the mechanical properties of which are extremely complicated. A granular system shows the characteristics of gas, liquid and solid depending on the kinstate of the granules. In the geological engineering field, some typical geological disasters, such as landslides, debris flows, are closely related to the mechanics of granular material. The key to seal with them lies in the phase transition of granular materials or geo-granular materials between solid state and fluid state. This paper first briefly introduced the fundamental characteristics of granular material. The jamming phase transition, local and non-local rheology, and couple typical experimental techniques. It also discussed the application prospect of the mechanics of granular material in geological engineering field. The success of integration of granular material mechanics and engineering geology would expand the research of physics and mechanics of granular matter and provide a theoretical basis for critical engineering and geological disaster prevention.