In this paper, the motion of the soil under dynamic loads is analyzed by constructing a two-dimensional discrete element model, and the stress and strain at any time step are analyzed. The simulation is made by using two different shapes of particles which are the disk particles and the elliptical disc particles, directed against the simulation of single particle in the past.And these two kinds of particles have different Poisson's ratio and elastic modulus.Using Hertz contact theory, the contact between disc particles, between disc particles and elliptical disk particles and between disk particles or elliptic disk particles and the surrounding boundary are discussed in this paper.The normal stress and the particle overlap of the specific contact are deduced.Finally, by changing the mean value of different dynamic loads, the "backbone curve" is obtained, and the dynamic constitutive model of soil can be obtained by the nonlinear simulation of the "backbone curve".