The three dimensional multiphase flow model and ind irect multiphysics model (including thermoelectric coupling model and thermal f luid coupling model) are developed to describe the variations of electric field ， flow field and temperature in the electrochemical machining gap. The electroc hemical machining of the internal spiral hole is simulated. Simulation results s how that the electrolyte velocity is fluctuant and decreasing， and the electroly te temper atur e as well as the void fraction of the hydrogen are increasing along the flow direction. According to the variations of temperature and the void fraction of hydroge n ， the electric conductivity of electrolyte is studied， which has a main effect o n the materia l removal . The analysis denotes that the electric conductivity of el ectrolyte increases along the flow direction. As a result， the material remo val rate (MRR) decreases along the flow direction which is unfavourable for mach in ing. A method of applying back pressure in the outlet is selected to d iminish the variation of electric conductivity of the electrolyte. Finally， expe rimental verification of the model using an in house built electrochemical mach ining system for the internal spiral hole exhibits good correlation with theoreti cal predictions.