Electrohydrodynamic (EHD) printing has recently received considerable attention for its potential of high resolution printing. In typical EHD printing, at the constant flow rate condition, the electric field applied between the nozzle and the electrically conductive substrate induces cone jet, so that a droplet smaller than nozzle diameter can be ejected. However, for real application, fluid should be supplied to the nozzle by the constant pressure for multi-nozzle EHD. In this work, at the constant back pressure condition in the reservoir, EHD jetting phenomena were observed changing bias voltage. In addition, the onset voltage for EHD jetting was measured changing glass capillary nozzle diameter (outer diameter: 23, 42μm), hydrostatic back pressure head on the reservoir and the distance between the nozzle and the bottom electrode.