Abstract: This paper presents the principle of interwell testing by electric potential for monitoring fire flooding front and the ground potential difference model, analyzes the impact of reservoir physical property and electrical changes in each zone on the formation resistivity during in?situ combustion process, and establishes the fire flooding front resistivity interpretation model by interwell potential method (IPM),by which the resistivity changes in objective layer is determined using the ground potential data, with the position of fire flooding front in the case study area. It is indicated from the downhole temperature and production performance analyses that the IPM can be used to detect in?situ combustion flooding front, advancing direction and velocity, as well as fire flooding sweep efficiency, and provide technical support for control of the production performance in heavy oil reservoirs