Abstract: The combined-charging hydraulic electrostatic spraying box was designed, the basic designing theories, structure and working process of this box were theoretically discussed, the atomization quality of this box was studied by carrying out performance experiment. The result of the studies indicates that for this box, the droplet table is narrower, the droplet diameter is smaller, and the atomization quality is better than common sprayer; the atomization quality of this box can meet the need of electrostatic spraying.