Permeability coefficient is one of the important parameters of the seepage characteristics of the graded gravel. The numerical calculation model of the gravel soil was established by the particle flow. The flow equation and pressure equation were used for coupling calculation with the response of deformation and stress. And the particles and fluid domain were coupled calculated, to obtain the stability condition of the whole system. The seepage was simulated to obtain the seepage coefficient of graded gravel. The results show that, the particles flow (PFC) method is suitable for the numerical analysis for gravel with any shape, size, unit assembly, and allows the element to crack and move. It is not necessarty to provide the macroscopic parameters of gravel. It only needs mesoscopic parameters, through the accumulation of mesoscopic results, PFC can simulate the appearance of the materials in the macro state. The permeability of the given 9 kinds of graded gravel are all larger than specification required, the permeability coefficient satisfy the requirements of engineering. Through the comprehensive comparison, it is better to choose the gravel 3.