The packing of fine particles plays a crucial role in determining the capture efficiency of dust removal devices in power plants, as well as in understanding the performance reduction of optical or power devices in aerospace engineering. Electrostatic forces, for its long-range characteristics and feasible manipulation, are widely used to control the packing of fine particles. In this paper, the packing structure of fine particles on collecting plate under high electric field is investigated by digital microscopy technology. The effects of pre-charging, pre-polarization, and external electric field on packing morphologies are discussed. It is found that the dipole-dipole force between particles causes the formation of long particle chains. The maximum length of particle dendrites during the packing is dependent on both the density of external field and deposit structure.