Dry EDM was a new technology with some merits to satisfy the production recently.The technology of 3D cavity was carried out by EDM milling using gas as the working fluid.The principle of dry EDM was discussed firstly.In this new process,the molten workpieee material was removed and flushed out of the working gap with the help of high-pressure gas flow.The advantages of this technique were little tool electrode wear and unneeded compensation online remarkably.During the process of dry EDM milling,the molten workpiece material was very easy to adhere to the machined surface,in order to solve the problem,twice machining was adapted,and the idea of split electrode was developed in a creative way.The experimental results show that the way is available to improve the quality of 3D surface.