In the measurement of water content of crude oil inside pipeline, the traditional electromagnetic conductance sensors cannot achieve the measurement of water content due to the influence of pipeline closure and electromagnetic shielding. In theory, the double-coil array electromagnetic conductance sensor can obtain the measurement of water content with low frequency sine signal as the motivation. However, its longitudinal resolution is too low and the characteristic is poor. The four-coil model has been established so as to improve the sensor vertical resolution. The simulation results indicate that the useful signal is concentrated in the internal of main coils, which plays a good role of longitudinal focus.