In order to simulate and control the distribution of oil and water, the authors used organic glass in place of oil. Experiments show that the relationship between electric resistivity and fluid distribution is not unique. This means that the most probability of fluid distribution must be found out when the inversion of crosshole electromagnetic imaging is done. The influence of fluid distribution upon electric resistivity is theoretically analyzed with the model of resistance in serial and parallel and numerically simulated with the ANSYS software, which gives a clear explanation of the experiment.