Water holdup sensor is key unit in production logging which is used to detect water holdup of crude oil in wells.In order to solve the problem of low resolution in the conventional water holdup instrument under the condition of high water content

propagation characteristic of electromagnetic wave on transmission line is analyzed

relationship between the dielectric constant and the amplitude and phase of electromagnetic wave at the end of the transmission line when it work under hybrid wave mode is deduced.The research shows that the method based on the amplitude character of the electromagnetic wave isn’t feasible for measuring dielectric constant

but it can be measured by phase character.Experimental research is carried out on this basis

experimental results are consistent with the theoretical analysis

the relevant data and conclusion has practical reference value to the structural design of the subsequent array imaging electromagnetic wave water holdup sensor.