Electrohydrodynamic flow in the system “needle–two wires” have been investigated using the Shadow method with simultaneous recording of transversal pumping intensity. Not–stable electrohydrodynamic flow appears as a fluctuation of central jet (flow from the blade) between electrodes that results in decreasing of efficiency of three electrode system. The possibility of electrohydrodynamic flow stabilization by means of decreasing interelectrode gap and using of additional, fourth electrode, which is situated behind the first two electrodes, is shown. Theoretical model of the pumping process, considering the flow as a diffuser flow from the blade, limited by two lateral eddies near the upper electrode–collectors, is proposed. As electrohydrodynamic flow develops, the average speed of diffuser flow as well as eddy dimensions are increasing. These two factors influence on the maximum flow rate of electrohydrodynamic pump. The maximum flow rate was found theoretically and the optimum parameters of electrohydrodynamic pump were established.