Abstarct: The separation and sorting of particles and cells have been attracting the attentions of many researchers for their applications in disease diagonstics and treatment. In this study the separation of paramagnetic microparticles has been studied using magnetophoretic force. Therefore, this study discusses the three-dimensional simulation of magnetic particles separation in a microchannel using two coils with horseshoe-shaped cores in COMSOL Multipysics 5.6. The sorting ratio of separating particles from a sample solution is an important parameter in in this field. The effects of magnetic field, velocity inlet, and the distance between two coils have been studied as effective parameters on sorting ratio. First the separation of M-450 and Myone particles has been investigated. The simulation results demonstrate that the highest sorting ratio reached the velocity of 0.4 mm/s and the magnetic field of 0.7 T. the distance between the coils was 740 . Then the separation of M-450, M-280 and Myone particles have been investigated. The simulation results demonstrate that the highest sorting ratio reached the velocity of 0.4 mm/s and the magnetic field of 0.78 T.