Motion of monosize particles and binary mixture in the reciprocating grate is simulated by means of Discrete Element Method (DEM). The flow behavior of monosize particles and the mixing and segregation processes of binary mixture with identical densities but different sizes subjected to horizontal reciprocating grates are investigated in this study. The spatial distributions of velocity and volume fraction of particles are predicted. The contact force and granular temperature of particles are calculated in a reciprocating grate. The mechanism causing the mixing and segregation of binary mixture is strongly dependent on the momentum exchange of each species which is related to the granular temperature of mixture components. The simulation results show that the translational granular temperatures of small particles are higher than those of large particles, indicating that the translational granular temperatures do not equilibrate for the binary mixture system. The kinetic energy of large particles is higher than that of small particles. The influence of amplitude and frequency on motion of particles is analyzed. (C) 2013 Elsevier B.V. All rights reserved.