Conical type plug valves are used as fluid controlling part of electrostatic pump.The flow quantity through the output and input valves is the same,but the pressure differences between the output and input valves under open condition are different,which depend on the pressure in inlet and outlet pipes.The smaller value of pressure difference was used for discussion,so as to ensure flowing unimpeded for another plug with larger pressure difference in any cases in order to achieve processing size consistency of conical type plug.According to the relationship between flow and pressure difference in fluid mechanics,a flow coefficient of 03 was temporarily used to calculate the flowing area in the annular gap and the flowing velocity.After setting the annular gap,the Reynolds coefficient could be calculated from these data,and the corresponding flow coefficient was estimated to be 0.26~0.7,which was close to or larger than that used in this paper before.Therefore，the specified flow and other related calculations can be ensured under the same condition of pressure differences.Proper choice of the cone halfangles for cone plug and cone-shaped tubes can ensure constant flow area in gap,thus the calculation is simplified.