In the process of ultra-precision grinding, workpiece can be ground with the arc area of the superfine and super hard arc-forming wheel. It is of great significance to study the precision dressing technology for super hard arc-forming wheels. EDM (Electron Discharge Machining) dressing can be the ideal dressing method for metal-bond super hard arc-forming wheel. Dressing device with pendulant electrode was designed. Polarity effects and the influences of different electrical parameters on wheel dressing efficiency and accuracy were studied in the experiments. The forming results showed that EDM dressing can satisfy the dressing requirement of arc-forming wheel.