Through the sputtering power analysis of field-emission electrons which hit on the end surface of positive electrode in single discharging pulse

the material wear mechanism of positive electrical discharging machining(short in EDM)process was studied

and theoretical prediction equations of maximum and minimum material wear ratio of electrodes were deduced too.A series of single-hole EDM experiments were designed and the experimental results show that

the mean discharging power produced by the electrode of copper is nearly 75 times higher than that of A3# steel when the other processing parameters are the same

and material wear ratio of the former is almost 10 times than that of the latter;both the machining efficiency and the material wear ratio of electrode increase with the improvement of valid work time and the pulse discharging power

and the increasing degree of machining efficiency is more significant than that of the material wear ratio of tool electrode.