Lack of effective monitoring techniques has become a bottleneck in the study on scaling problem in soil science and hydrology. In recent years, some geophysical methods, of which Electrical Resistivity Tomography (ERT) is representative, were introduced into the researches on soil hydrological processes in vadose zones, which provides a new strong tool for solving the scaling problem. Coupled with the petrophysical relationships between soil electrical resistivity and other soil properties, ERT can be used to realize multi-scaled non-destructive continuous monitoring of soil properties or states. In this paper, a review is presented of the basic steps and characteristics of ERT, and its applications to the studies on soil hydrological processes. At the same time, in-depth discussion was conducted of problems in and potentials of the application of the ERT technology to the studies on soil hydrological process in vadose zones.