Firstly, three kinds of sand pile experiments which reflect the universal process of energy dissipation within the slope accumulation under the self-organized action are reviewed. They all show that self-organized criticality (SOC) is related to granular non-uniform. The experiment of Tokamak plasma system is introduced, which shows some of SOC properties of Tokamak plasmas in Ohmic region or L-mode. Secondly, material tests in geotechnical engineering and numerical simulations of micro-structure of sand piles indicate that SOC is determined by the structural characteristics. Finally, according to the principle of SOC, the behavior of slope disasters under gravity and its forecast as well as the design of protection engineering are discussed.