This study reports a numerical simulation ofseparation efficiency of microparticles in the divergent microchannel flowusing the Eulerian and Lagrangian methods. The flow field, ion field andelectric field are simulated numerically with finite volume method first,then microparticles are injected from the inlet of the microchannel andtracked with the Langevin-equation-based model, in which dielectrophoreticforce is included. It has been found that the microchannel's pumpingcapability increases with the increase of divergent ratio (ER). In addition,the effective separation length between microparticles increases linearlywith the increase of ER. With and without consideration of Dielectrophoresis(DEP), the ration of ESL to ER is 5.9 and 4.79, respectively. Itmeans that thenegative DC-DEP always reduces the separation efficiency in the divergentmicrochannel. The aforementioned conclusion is helpful for the designoptimization of separation apparatus.