In the gas-solid fluidized bed reactors, the interactions between particles and the wall, the gas, or the other particles always generate electrostatic charges, which affect the flow characteristics significantly. Imposing an external electric field to regulate the particle charging and reactor hydrodynamics is a potential way of process intensification. This work focuses on the incipient gas-solid fluidization under external electric fields of direct current (DC) or alternating current (AC), with each in the form of cross-flow and co-flow respectively. The two-dimensional multi-fluid CFD model coupled with electrostatic model is established to simulate the electric effects on the fluidized bed hydrodynamics. As the particle charge magnitude increases, the bubble size and bubble detachment time are reduced, while the electrostatic force on particle is enhanced obviously. By imposing the DC electric field, the bubble is split in cross-flow field and stretched to be sharper in co-flow field. Meanwhile, the particle self-generating electric field and particle velocity are strengthened around the bubble, distributor and wall. For the application of AC electric field, the bubble deforms in the lower frequency field, and the particle self-generating electric field declines near the wall, which will reduce the particle segregation and agglomeration towards the wall. (C) 2015 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.