Temperature distribution of singl e pulse in spark erosion is simulated by Ansys. Simulation results demonstrate t hat w hen the pulse duration is very short， the proportion of vaporization is hig h， but the productivity is low. Long pulse duration will result to a high productivity， but lo w pro portion of vaporization. When pulse duration is extended and the channel moves， the volume and propor tion of vaporization are all increased compared with machining in static dielectric. Therefore， high pressure dielectric is intr oduced. E xperimental results show that the channel indeed moves. After being machined， the product is gathered and weighted， and the productivity is about 1 g/h.