In electric discharge manufacturing, especially to the complex part finishing machining, electrode wear effects the electrode’s life-span and the work pieces precision in both dimension and geometry. Although it is more difficult to explain the exact mechanism of metal erosion in sparking, the basic phenomenon that the work materials near the channels melted, vaporized, and then flushed off in the dielectric liquid has suggested that the mechanism of electrode wear is based on a thermal conduction process governed by heat generating from arc channels and dissipating into the tool and the work. On the basis of a review of the other researchers’ work and analysis to the thermal conduction phenomenon, this paper presents an electrode wear model based on heat conduction. Finite element is employed to solve the heat conduction model of wear, and in addition, a theoretic planar sunken function at electrode surface impacted by plasma flow is established. Some experiments and simulations are made to verify the hypothetic model, and the conclusions that the simulation result of erosion figure and erosion trend of the material are correspond to the hypothetic model are confirmed.