Abstract: In order to determine the effect of an external electric field on bipolar agglomeration, this article has solved the electro-hydro-dynamic (EHD) flow in the electrostatic agglomerator using FORTRAN code and calculated the charge distribution of particle in statistics under a certain EHD flow. Also, with an external electric field, the collision and agglomeration between bipolarly charged particles has been investigated. The presented results of calculation show that only the ratio of the electric field force to the drag force on a charged particle is near to 1∶1, the external electric field can significantly affect the bipolar agglomeration. The larger the particle is, the more collisions between bipolarly charged particles occur under external electric field.