An appropriate technique for separation of particles in microfluidic system is the use of dielectrophoresis (DEP), a phenomenon referring to the motion of a particle in a non-uniform electric field due to the unbalanced electrostatic forces on the particle’s induced dipole. Therefore, in current study, separating platelet cells from red blood cells in a continuous flow using dielectrophoretics (DEP) mechanism is numerically investigated in microfluidic device. To this approach, COMSOL Multiphysics software is used. To verify the simulation, the results are compared to previous experimental data. The effects of different parameters including voltage, flow speed and frequency on the separation of platelets are studied in details. The results reveal that successful separation of platelets from blood cells are occurred by applying voltages. Low voltage causes platelet cells and red blood cells to exit from one side of the channel while high voltage causes the red blood cells to collide with the channel wall. According to condition, a range of voltage is suitable for current device to efficiently separate red blood cells and platelets. Also, with increasing particle inlet velocity, the separation takes place farther from the inlet, and the distance between the two consecutive isolated particles of red blood cells or platelets increases.