Abstract: The collapse of static granular pile under gravity is the basis for understanding many human processes and natural phenomena. There are some difficulties for the traditional simulation methods, such as large number of single particle tracking, obvious rheological characteristics, and complex phase evolution of macro simulation. Based on the physical mechanism of different phases in granular media, the concept of full phases is defined and divided into three regions. According to the stress-strain relationship and volume fraction of granular media, the existing theories describing each phase are effectively combined by determining the coupling relationship and transformation criteria between different phases, and the coupling model theory describing all phase states of granular media is established. Then the physical model of granular media is solved with the strategy of coupling smoothed discrete particle hydrodynamics and discrete element method. The coupling and transformation algorithm between different phase particles is clarified and the particle size independence of the diameter selection of the initial SDPH particles is tested. The numerical simulation of collapse process of granular pile under different aspect ratio is realized. The calculated results are in good agreement with the experimental results. At the same time, compared with the discrete element method, the amount of calculation is controlled. It not only captures the different phenomena of deposition after granular pile collapse under the influence of different parameters, but also obtains the effects of different conditions and parameters on the spreading characteristics of granular pile after collapse are obtained, which provides effective support for revealing the complex motion mechanism of granular media widely existing in industry and nature.