The state of tool workpiece contact zone in Electric Hot Machining(EHM) is different from that of conventional cutting. This paper investigates the electrothermal state and its characteristics of tool workpiece contact zone by analysing the electrophysical phenomena in EHM, which has some instructive significance to studying cutting mechanism, electrothermal characteristics, and wear mechanism of cutting tool in EHM, and practising the state control during the processes of EHM.